If she had lost a large amount of weight due to the proper care before you recieved her, her body and organs may be filtering out alot of the antibiotics. Has she deficated at all? Any eurates?
She may have lost alot of weight but i don't know the back-story so i'm just throwing stuff out there that could be completely wrong :/
She's been here a little over two weeks and nothing yet. I know she hasn't eaten in probably 6 months but I don't know about her weight. (again, I know the previous owner and he is one that thinks they can live forever without eating and proper care. When he lost his 11 yr old, you'd think he would have learned)