As these girls show, there isn't one set formula for sexual identity.

"One same-gender experience does not necessarily make you a lesbian or bisexual," says Schroeder. "At the same time, that one kiss can confirm feelings a girl has had for a while and may not have been aware of or accepted yet."

Schroeder says that "teens would love it if there was a checklist they could go down, mark answers to, and then score to see whether they are heterosexual, lesbian or bisexual. But it's never that easy. Feelings of attraction are discovered, not decided upon."