When you think about it, we actors are kind of prostitutes. We get paid to feign attraction and love. Other people are paying to watch us kissing someone, touching someone, doing things people in a normal monogamous relationship would never do with anyone who's not their partner. It's really kind of gross.
I have to really enjoy someone's personality, not just their looks, before I'll kiss them.
I feel much safer with girls, so I felt more comfortable kissing her in the movie than kissing any of the other people that I had to kiss.