What's this (romantic comedy) film?

well, romantic comedy, quite old (late 90's) i think, where 2 girls fall for the same guy. I thought it was Cameron diaz, but cant find it, so not sure now. Anyway, one is 'ugly' and one is beautiful, and the ugly one doesn't think she has a chance, and the pretty one is supposed to be helping her but ends up getting off with him. Any ideas?