Hi E.,
I had/have the same problem with 2 of my children; daughter, 16, though not as much lately, and my son almost 9.
I used to use vaseline to keep it moist. It worked well, but my daughter likes some 'flavor' to her chapstick. I have been using Carmex since I was a teen and began buying her some of her own. She uses it a couple times a day to keep from getting that bad anymore - she hasnt had it that bad in about 3 years. Sometimes it has to burn a little, but only because of how sore it gets - you need to do something to make it better, unfortunately, some remedies may be uncomfortable.
My son, however, never remembers to use his Carmex until its too late. Then I have to remind him a couple times a night; before school, after school, after dinner and before bed.
I try to be sure all of my kids have their own chapstick - and at least 2 to each of them; one in every coat and 1 in their book bag/purse. And remind them not to share with their friends.
I also started using it on my little ones cheeks when they go outside. It keeps them from getting chapped also.
Chapstick brand also works, but seems a bit 'waxy' and nobody in my home likes it. Blistex is strong so we dont use it often. Carmex comes in a little canister, a squeeze tube and a twist up tube. Its not too strong, has a nice scent/'flavor' - its our favorite and it doesnt hurt.
Hope you can find something that works well for your daughter.