No, because the flat iron will not be close enough to the scalp where the nits are. Besides, you really don't want to increase your chances of buring your child. Your best bet would be to have her wash her hair and condition it really good. With hair still wet, use a nit comb to comb out all the nits. You'll want to wear gloves while doing this and use a metal comb, not a plastic one. It will take several hours to go through the hair entirely, especially if her hair is long. Wash all bedding and stuffed animals in hot water and dry on high heat. Vacuum as well. Lice can be extremely tough to get rid of, but if you make sure that all the nits are pulled out of the hair, then your problem will be gone.