Here are a few basic things that could help with painful moontime:
Magnesium supplements can really help to relax any smooth muscles in the body, including the womb. Be careful not to go overboard though or they will relax the bowels, though sometimes that's needed too!
Cramp bark works but has to be taken every couple hours consistently. May not be practical for a teen.
More good oil (omega-3's, as in fish, flax) and less "bad" oils (omega-6, as in canola,...