I'm a fair skinned person that doesn't tan and I get sun poisioning or 2nd degree burns if I'm in the sun too long. At one point I had to have prescription sunscreen as a child.

While I don't have a teenager of my own, I certainly remember being one clearly. As a teenager I hated wearing sunscreen and fought with my mom (whom I'm very close to) many times over wearing it. In the end mom had other things she'd rather go to the mat with me on and let this one slide. After getting badly burned or embarassing red spots from not wearing sunscreen I eventually learned to put it on myself with no prodding.

The way I see it you have two choices:

1) MAKE your daughter put it on every day before she's allowed to leave the house, even if it means she's late for school because she's fighting you on it, you are the parent and have every right to put your foot down when it comes to something important, someday she might thank you for your stubborness.

2) Choose your battles, if there are other things with higher priority that you are battling her with right now (ie; curfew, boys, drugs, smoking etc) then a battle over sunscreen pales in comparison. You can't go to the mat on every issue or eventually she'll just learn to hide many things from you.