Sisef (n): A girl who considers having most or only guy friends a badge of honor/ tends to mention casually in a group of all girls who happen to be friends, often as an excuse for not being close to any of them and/or a way of distancing herself from Girl Talk: "Oh, all my friends are guys!"

Dialogue:
Non-sisef: "Omg, Mark is sooo cute!"
Sisef: "Oh my god, that's so wierd to me- Mark is, like, my one of my really good friends!"
See what we mean?