Crying for her sister, is it a puppy thing?

The crying could be separation anxiety.  I'm not an expert on how to handle it with a pup though. 

I would be careful not to take her out of the crate when she cries though.  She will have trained you that's what works to get out.

She may need some extra attention when Coffe gets adopted.  If for some reason the lady doesn't take her...you might want to take some steps to do things separately and alone with Piper so she learns life is ok without Coffe around.

My Lab Cody (rip), had SA but she did do much better with another dog around...it wasn't as traumatic for her when I or DH left the house. 

I never take her out when she cries. She will whine for a couple of mintes but onces she stops and is calm I take her out and put her with her sister. Hopefully everything will go well tomorrow.

oh ya... seperation anxiety! mine are like that. jason more than moca.

you really have to get them use to being on their own! when i take them for walks i take them seperately. which means, one of them has to stay behind all alone! it's part of getting them used to it.

i know there's probably no time, but in case they dont get adopted, you should start speerating them more and more, to get them used to it, since you want them to be adjusted to being alone as much as possible, so they are easier to adopt out, right?

google seperation anxiety (sorry, i'm leaving for an interview soon, so no time to explain).

it will give you ways to deal with it for seperation anxiety from being seperated from humans, but with dogs you can basically deal eith it the same way...

I will start today with that. I have to go translate today and I will keep them separated its only for like 5 hours hopefully my little sister will be here to let them out for potty. If the adoption fails than I will separate them Piper will stay in my room and Coffe will go in my brother's room.

Definitely follow Callie's advice about taking them out separately.  Raising litter mates together is tough, because you want both dogs to be more engaged with you than with one another, and of course, they speak the same language and are just learning yours!  My advice would be to board them overnight separately (even if you aren't going on a vacation), take them to obedience class separately, walk them separately, and feed them separately.  A lot.  Don't give in to whining, and don't put them immediately back together (or they may learn that whining wins them whatever they want - then you really will have a problem),

They will stay in separate crates from now on and will go outside separate. I can't board them because Coffe might leave soon and I don't have the money. Hope everything goes well from now on. Thanks for the advice!