Personally, one gets a smoother, softer look and feel with natural hair when using a hot comb over a hot plate. Provided that you are testing the comb with a paper towel to make sure it is not too hot, your daughter's hair should be fine.
My mother pressed my hair with a hot comb from the time I was about two years old. I received my first relaxer at age 22. My mother would wash and condition my hair, and then plait it into five sections. She would then begin to press my hair when it was still slightly damp, believing that some moisture left in the hair aided the pressing process.
The secret to a good hot comb press, I believe, is using the back of the comb. Additionally, doing an initial press, just to get the kinks out, followed by another light press once you have added a light oil, conditioner, or good old grease to the scalp, massaged it in well, and then comb or brush the hair through, also makes for a good, lasting press. Last, having two hot combs also facilitates the process.
northernbelle