I'm going to be traveling with a 15 year old. What form of identification do I need for her?

If she had a school issued ID or a permit. Those would be fine. My wife used her Costco card once and they let her through so when it comes to identification I thinks it is more lax than people think. You only need to worry when you have a lap child or infant to provide info like a birth certificate or immunization records.

I think Brandon Taylor covered it.🐱

Good narration Brandon Taylor