I’m guessing this movie was made in the 90s.
All I remember about it is that this girl was always putting lip gloss on and in one scene the lipgloss girl takes this girl that has a broken leg out on a boat. I think I remember the lip gloss girl seducing the broken leg girl and they end up making out. The lip gloss girl pushes the broken leg girl off the boat and leaves her to drown.
In a later scene, another character is on the boat and finds the girls lip gloss and realizes she’s the one that killed the girl.