There are several different types of biofeedback.  My daughter (21) has been suffering for over ten years and not only have I worried about medications side effects, but the fact that even with those risks we have not found a formula that is effective and of late it's been worse.  Her doctor took her off all triptan and pain meds and we are doing a detox and only trying a new preventative (gabapentin) for 2 months in hopes that the migraine frequency willl decrease enough that she will only need triptans a little instead of 4 times a week.  Sorry - long story short - we are trying alternative therapies as well over the next 2 months, one of which is a biofeedback therapy called Ondamed.  It's too soon to tell how well it will work, but my daughter likes the therapy.  You can google Ondamed to find out more info about it.  My heart goes out to you and your daughter, being so young and having migraine is so difficult - I wish relief for both of you.