
Oh dear. It sounds as is the 'honeymoon' period is over. :(
Rehomed/rescue dogs often go through a nightmare time once they feel reasonably settled. There are several books specially about rescue dogs in bookshops and petshops. It would be worth your getting as many of these as you can, as these dogs have their own set of problems.
In the meantime I would make sure she is not allowed upstairs, or on the furniture. Get her to sit, down or give a paw before she gets her food, or attention, or anything she wants. But don't be confrontational about it - be cheerful, amtter-of-fact and determined.
Why was she being rehomed in the first place?
Good luck.