Problems with new dog

Oh dear - this is why pet shops should not be allowed to sell puppies.  Chances are she has come from a puppy mill and has not been well bred or had good early socialisation.  Her parents were more than likely less than healthy with unsound temperaments and they will have passed these traits on. 

It's such a shame and must be so hard for you but please don't compare her to your previous dog.  I am sure your intention was never to replace him anyway.  Even if you had got her from a better source (a reputable breeder), she still wouldn't have matched up, it sounds like Beau was one in a million!

Nipping and mouthing is common and normal in puppies and retrievers are no exception.  In fact they can be one of the worst offenders.  The name gives you a clue - as "retrievers" it is doubly natural for them to play and explore using their mouths.  Their dam and littermates usually begin teaching them "bite inhibition" at a very young age but this is incomplete when you bring the pup home (am I right in saying she was 10wks when you got her?)  What did you do to teach her this when you brought her home?

I think the best way is to make a sharp yelp the moment her teeth touch your skin and then offering her something she is allowed to chew on so you can praise her well for that.  She needs to chew SOMETHING and without the redirection she will carry on regardless.  After several days, stop offering a chewie to replace your hand so she doesn't begin to see you as a giant walking dog chew vending machine - just yelp (OUCH) and walk away, withdraw ALL attention till she calms down.  Do make sure there are plenty of safe things she is allowed to chew on and make sure to praise her any time she makes use of them.

That is what I would do for a young puppy, but at 7mo it will take longer and you would need the consequence of her action to be more severe to counter the time this has become ingrained.  We used to have a bull terrier with dreadful bite inhibition.  In the end we solved it by yelling OUCH (as above), and OUCH was a signal for every person to get up and leave the room for 30sec-1min or so without speaking to or looking at him.  We'd return just as quietly, ignoring him.  If he was well behaved someone might call him over for a fuss or play but we'd repeat the instant teeth touched skin.  You could try this and see if it works for you.  I really don't like the idea of squirting lemon juice in her mouth though. 

She is teething - what are you giving her to help with this?  Freezing some of her chews/toys is a good idea.

Has she been to a puppy class?  The other puppies there would have helped enormously with teaching her bite inhibition.  The opportunity for free play interspersed with training is a MUST for any puppy who has just completed his vaccinations, it's so important for training, socialisation and proper development.  Is she in a class now?  If not, get her booked in ASAP!  But go along to a class without her first and make sure you are comfortable with the methods used.  Go for one that uses kind positive methods.  At 7mo she may be a big girl but shes stil a pup and should not receive harsh treatment.

How much exercise does she get?  What other stimulation does she get, what kind of training do you use?  Clicker training is HUGELY stimulating for dogs and its fun for both of you.  It will improve her obedience and bond with you and help tire her.

Yes it is normal for her to ignore No.  "No"  is a bit of a swear word in dog training.  The way dogs learn is very context specific and many can't cope with NO being used for "stop biting!", "don't jump up"  "get off there!"  "dont eat that"  "stop chewing that!"  "dont dig the flower beds!"  "stop chasing the cat!" "get out of the bin!"  "don't wee there!"  etc.  Rather than telling her "no"....
1.  Ignore her if what she is doing is merely pesky - like jumping up.  If she gets no reward, she will stop doing it.  Even a reprimand or a SIT! can be construed as a reward.  (If she is jumping up, turn away, fold your arms and look at the ceiling.  If she continues, walk away.)
2.  If you need to stop her from what she is doing, go up to her and lead her away from it calmly.
3.  If she knows a command and is reliable with it (by that I mean will you know she will respond to it in any situation - don't forget "context specific", has she had practise in lots of situations?) then ask her to do something incompatible with the undesirable behaviour.  Getting a dog to DO something is much easier than getting her to STOP doing something.

In answer to your final question YES.  My second dog was a nightmare - or so I thought.  I realised just how much my first dog had "spoiled me" for all other dogs, how easy he had become, how steady.  Puppies are hard work anyway, but in comparison to a steady well behaved dog they seem little monsters!  But I realised that most of what the dog was doing was normal puppy behaviour and in fact the problems were of my own making - I had inadvertantly taught him to be that way.  When this light bulb switched on for me, things got a lot easier.  I stopped thinking I'd got a "bad dog", I changed the way I did a few things and he started to improve.  The important thing to remember she is a puppy, set the bar low for her and make it easy for her to succeed.  Don't set yourselves up for failure!
 
Is she crate trained?  If not I highly recommend you get one.  Search the forum for info on introducing the crate to her and never use it as a punishment.  The crate will help give her structure, make her feel secure, help her to relax and give her somewhere to go when she is stressed or tired.  She can be shut in for short periods when you are unable to supervise or when she is being hyper and you want to calm her down before she starts nipping.
 
Lastly, do you use NILIF?  If not, google it (or search the forum) and start making her work for everything good in her life.

I'm very sorry. Just one word, not directed at you (please do not take this as a rebuke for something that's done already) - for anyone lurking out there - this is a good example of what the pet "industry" does to dogs. Overpriced, underbred, and not screened for temperamental or health issues.

Okay, back to your pupper, who now lives with you and we'll deal with this as best we can.

Your dog is at an age when even the best dogs can be fearful. On top of that, it sounds like your dog doesn't have good coping skills to begin with and not much confidence. First of all, it would be best, I believe, if you stopped punishing her wtih scary stuff like chains and lemon juice. Your goal is to get her thinking through her actions and not adding to her fear.

Make a list of the situations that make your dog uncomfortable. Think of events carefully and objectively and try to sense patterns. They won't ALL be alike - you may have categories like, "My dog growls when strangers come over" or "My dog tries to hide or run when I pass a strange object on walks" or "My dog barks frantically when we're in the car and we go through a drive-thru."

If you end up with a really long list even after grouping some of these together, consider very seriously going to a certified applied animal behaviorist. Here's a national directory -http://www.animalbehavior.org/ABSAppliedBehavior/caab-directory If no one is near you, you can call and some will give phone consults, and some will refer you to someone qualified in your area.

If there's only a couple categories, your dog is probably young enough that she can be helped fairly simply. She may never be a perfect dog, but remember that your first dog is almost always the hardest act to follow. Try to let her be her own dog - learn to look for what SHE has to offer you as her personality matures and blooms (at seven months old she's not much more than an obnoxious teenager, lol).

I had a dog with SEVERE problems and she was quite functional with a great deal of work. I learned a lot more from her than from my heart dog, who is perfect in every way (lol). We did flyball, agility, a little obedience, frisbee, and herding competitions - and even though she had to leave here, I still think about her a lot and I'm proud of her work today making sure air force pilots are safe from birds hitting their planes and causing accidents (she chases birds off military air base runways).

Good luck! Feel free to post with more details.

First of all, I am so sorry for your loss of Beau. No dog will ever replace him, I'm sure. As for Stella, many people here can give you lots of good advice on training, I'm not sure what Bark Busters is or chain throwing, maybe they know. Most people here don't advocate getting dogs from pet stores because oftentimes they are procured from "backyard breeders", which is to say people that don't carefully breed their dogs to avoid problems like health issues, or sometimes behavioral issues as well. What you're seeing with Stella, I would venture to say, is the result of that. But she's yours now and you sound committed to her, which is a marvelous thing. Think of it as having a child with special needs. You will probably have to do more with Stella to get less than you did with Beau, in terms of behavior and positive results, but you can still develop a bond with her. There have been other threads here about the woes of new pups (and puppyhood can last a couple of years!). I, or someone else, will get you a link to those, so that first off, you won't feel all alone in your "buyer's remorse". A lot of people like the clicker training, but if you're like me, you need someone to show YOU how to do it! So I would suggest enrolling in a puppy basic training class right off the bat. Lots of places have them, but make sure you have a good trainer, and I bet people here will be able to give you advice on what to look for in a trainer. You can learn a lot from this site, and you can get a lot of support too!