Feral cat was accepting but has now regressed

Question
I trapped a feral siamese mix cat, had her spayed and given all shots and deworming. Also had her tested for feline illnesses. Vet suggests she is approximatly 9 months and I was told she is FIV positive and I sould consider euthinizing her vs keeping her, or relesing her. While she recovered from her surgery I spent time with her and within 3 days she allowed petting, she then wanted me and my husband to pet her. She also laid down on our feet and allowed petting of her chest/neck, and she purred. Then a week ago I had to take her back to the Vet, for him to draw more blood for the Western Blot test. Since bringing her home she no longer wants anything to do with me or my husband. She looks fearful of us &/or very unhappy. Will she come around to the way she was before the last Vet trip?  If so, any idea how long it will take? I have another cat who does not have the virus, so our little feral stays in a tiny guest bathroom. I am loath to release the feral back to the park I trapped her at because she was in a sorry way (under fed, looked scared all the time, etc.) Any suggestions as to how I can gain her trust again? I feel so sorry for this poor creature.

Answer
First of all, I want to stress that you do not want to release her since she has that disease and can spread it to other cats.

Second, it sounds like she is taking out her frustration on you for the second visit to the vet. The thing with cats is you can beg and plead, but if they refuse to respond, the only you can do is sit and wait for them to come around. Do simple things like pet her when she lets, but after that let her come to you. There is no time frame for her behavior as cats will be cats and they'll come around only when they want to.