Sick Cat what is the prognosis?

We took in a stray recently. She went to the vet and had all of her shots and blood work done and she was spayed. She is FIV and Feline Leukemia Negative. She was diagnosed with an upper respiratory infection and Chlamydia of the eye. She also has Giardia (parasite). She was severely underweight too. She finished her antibiotics for her upper respiratory infection and her Giardia Medication. I am noticing though that when she purrs really loud she still sounds congested a little bit. Do you think that's ok? How long does it take for a cat to clear up the infection. Also, now that she is finished with her giardia meds do you think that she will start to put on some weight?