Hi H.,
I am a bi-racial woman. My hair is also pretty thick when it is natural. It is VERY curly!! I have used just about every relaxer known to man (children's and adult)and have not been happy with any of the results. They were either too weak or way too strong, both ruining my hair until it grew out. I have learned the hard way, to just leave it alone! I keep my hair curly in the summertime because no relaxer can get rid of my friz when the humidity hits or the waves at the roots. In the winter I keep it straight so I don't go outside with wet hair. I recently received a hair dryer that staightens my hair wonderfully! It is the Infiniti Hair Designer by Conair. I love it!!! Before I would blow it out, then use the hot comb to flatten it and then a curling iron to curl and soften the ends - all this took 1.5 to 2 hours (I had to do this with or without a perm). With this dryer, all I do is blow dry it in 2 inch sections, and I'm done in about 30 to 45 minutes. It comes out really nice, full and soft {bouncin' and behavin'!}No hotcomb, no curling iron - less damage, less money (no salon!). If I don't have time to dry it, I can just wash it and go since it will still curl because I don't have a relaxer.
Hope this helps. I remember those teen years, I absolutely hated my hair and was always trying to change it, but I always made it worse. I'm sure your daughter is beautiful, curly or straight :)
~J.