I always saw sleep the same as eating, I'm not going to make it a battle. I can't force someone who isn't tired to sleep, but there were things I could do.
If my kids weren't tired I'd let them stay up later, they'd get another 30 minutes and if they still weren't tired then they could lay in bed and read for another 30 minutes. This kind of thing happened with all my kids except my middle one, he loves his sleep LOL. I just chalked it up to the normal sleep pattern changes that happen, and it seemed like it was because they pretty much feel in to a routine that worked.
My dd was always a night owl, she comes by it naturally because me and dh are, or at least I was before 40.
If you are sure there is nothing going on with her, and I would ask her not rely on the teacher knowing something, I'd try to change the bed time routine and see if it helps.