I am so sorry to hear that your daughter has these issues.
I have a simple perianal fistula, and my doctor placed a seton, and it made a lot of difference in how I feel and stopped the fevers i was having, though it's a palliative, not curative measure. And no, in allll the years humans have had fistulas, there really isn't any great advancements in their treatment. I will likely have my fistula and seton for months to years, but again, I feel way better with it in than I did without it. I don't even feel it 95% of the time, anymore. I never had stool drainage; it's been just mucus and blood, but mine doesn't involve my pouch at all. A small 2X2 is all I wear, up against it, for comfort.
If your daughter has perianal Crohn's disease, biologics like Remicade sometimes will help a fistula heal. Sometimes antibiotics help, sometimes immunosupressents. Active Crohn's in the perineum makes surgery a bad thing for those patients, because they tend to heal too slowly there. I'd say a seton or two is her best option to start with. It allows the fistula tract to drain without the skin healing over, and the tract can mature and the inflammation around there can lessen. The body no longer sees the fistula as a wound and only recognizes it as its own tissue, which is why our bodies won't "heal" them on their own, and that stinks. Setons were created by Hippocrates; tells you how much advancement has been made.
I feel like I'm going to have this rubber band in my butt FOREVER, and I just might, but I'm "old" now, with a loving husband, and my childbearing years are at their end. I feel for her to have to go through this in her late teen/early adulthood days, when intimacy and body image are so important. Can she find a support group for perianal Crohn's sufferers? I know two boys on my block are going to a Crohn's/colitis camp this summer... Perhaps talking to someone going through it, too, will help, especially if they're in her age group.