I'd stay home -- you'll go and resent the time she is off cavorting with island boys. Trust me, she might not plan on doing that, but if she's known for that.... well, the surf, the sand, the annonymity (sp?) she'll be running around after the guys and forgetting you're there. I've been there, done that with my friends in the past.

Why not find a friend who feels the same way you do about drinking and meaningless flings, and take them along? You'll have much more fun because you'll both be awake for the fun stuff on the beach while your party-hearty friends are sleeping off a night of too much booze.