Toobusy, so sorry your daughter is still having problems. I have a pouch-vaginal fistula - like your daughter's (I think?), my fistula comes out just outside the vaginal opening. The fistula finally was dx'd 2-1/2 yrs ago, and I have had a seton in for a year. I was on antibiotics for approximately 2 years, I don't know if they helped or not. I quit abx's about 2 months ago and am doing just as well, if not better, while off of them.
As in Rachel's case, the seton has absolutely improved things - prior to seton placement, and for the first 8-10 months after seton placement, I had drainage - mostly pus, and some blood. FINALLY, a yr. later, things seem to have calmed down, knock on wood. My surgeon (Cleve. Clinic) said she would not even consider a repair unless a seton was first placed: things do need to settle first, the area around the interior opening needs to heal as much as possible before any kind of repair will "hold". I have not made a decision on my next step ...
I too am "older", am married, and thus am not in the same situation as your daughter. I was told by my surgeon and by Dr. Shen that I/c would not damage the fistula - however, at least in my case, there is discomfort so we find other avenues. I am sorry she has to be in this difficult situation at her age.
On a hopeful note, Ginlyn has had mesh from pig muscle used as a repair, and as far as I know, it has held. She is out of the country, but please look her posts up for further information.