No way. I have naturally curly thick frizzy hair and she will ruin her natural curl pattern. I'd allow her to get her hair straightned for special occasions, but not regularly. If she wants it that bad she can figure out how to do it at home. She can easily figure it out on youtube.
Most importantly, I would encourage her to do some research on curly natural hair care. There are so many great products and tools that can help her have popping curls - frizz-free, moisturized, shiny and bouncy. As a kid of the 80s, I can tell you the hair game for curly girls is 1000% times better than what I had access to back then.. Trust me, she can't even imagine how good her curls can look with the right products and styling tools.
What type of curl pattern does she have?