Like someone I don't know??

[Bob]

I like this girl who lives in a town 20 minutes from me. I went to school with her older sister but have never met her sister, but see her on social media facebook, twitter, instagram. She is going to college in my town next year and I will be in town but at a different college. I have never spoken to her before, but I find her very attractive and it seems we have stuff in common. I want to friend her but don’t know how to talk to her since she doesn't know me?

[Ariana]

Be causal and approach her. Probably start by saying I know your sister Amanda (Whatever her name is) and I just wanted to say hey. Something not to creepy but something friendly to kick off the start of a new friendship and hopefully you guys get friendly and close. And see how things happen from there !