poor eyesight

I would definitely have her checked out by your vet.  A three year old dog doesn't usually have these types of problems without an underlying condition.  I would have bloods ran, as well as a urinanalysis done to rule out diabetes.  Undiagnosed diabetes can cause blindness.

Having her seen by an opthamologist would also be a good idea.

Poor girl.  I'm sure that not being able to see her surroundings is very stressful.  For now, I would keep her leashed so that she feels more confident, & so that she can learn routes to get around the house & yard.  For some rescue dogs, six months is still very soon for them to feel totally at ease.

Good luck!

Yes, Vet check first if you haven't already.  Also, this site may offer you some help and support in dealing with a blind dog.  I had a dog that went blind in later years but she had been with me since puppyhood so her transition wasn't difficult.  I'm wondering how your dog is indoors, confidence wise? 

http://www.blinddogs.com/

 Yes, definitely have her checked by a vet. Sometimes these things can be fixable depending on the issue, or at least managed so they don't get worse. That said, I'd do some research on google - I've heard good things on using scents to tell dogs where they are within the home... so using several different scents or essential oils, and using a different one for each part of the house or yard (and only use one for each area).