Like I said before--there is no cure for those nasty SM's (stretch marks)--time will make them fade but nothing makes them go away.
I just wanted to write and say that I can ssoo relate to your daughter. I went from 0 to B cup overnight it seemed. I was braless at the end of 4th grade and DEFINATELY bra-ed by the start of 5th grade. To this day I won't show any cleavage because of it.
Just make sure she has a strong sense of who she is INSIDE and the OUTSIDE becomes less important. A beautiful OUTSIDE can change so fast for what ever reason but a beautiful INSIDE lasts a life time.
Give her my love
-from one who's been there!