Gina Gershon had the look that lesbians were totally into (she had some similarities to Angelina Jolie), and in fact played bisexuals/lesbians in a few movies.
However, unlike many women in Hollywood, she was actually straight. She even said in an interview that she "wished she was lesbian", but wasn't at all.
She must have been pretty good at her job, because for years I believed she really was a lesbian.