Tell her there's a girl you like, but you're too nervous to talk to her.

You sigh. "Well... there's one girl in particular that I'm interested in. She's in my English class. I haven't got the nerve up to talk to her though. I don't think she even knows who I am." You explain to your sister. "I'm kind of pathetic, aren't I?"

At that, Abbie looks you right in the eye. "No. You're wonderful. You just don't know how great you are." She tells you, sounding as sincere as you've ever heard her. "If you ever talked to girls besides me, you'd see that pretty much any of us would be crazy about you. Your problem is you live in your head too much." She says, as she leans towards you and her hand moves to rest on your thigh. "You should think a little less, and just do something. If you see something want, just go for it." She gives your thigh a little squeeze as she says that. The intimate touch and the view down your sister's shirt are making you feel a little sweaty. You can feel your cock getting hard, and you're worried that she'll notice. "Talk to that girl today. Ask her to go out with you this Friday. What's the worst that can happen? If she says no, you won't have a date for Friday, and that's the same as if you don't ask at all, so you lost nothing."