crush on my friends sister ?

That you don't have the guts to say hello to her face.

Seriously, you have the perfect means of getting an introduction. Spend time with your friend and you will eventually meet her.

Or, go up to her and say "Are you xyz's sister?"

You've got an automatic conversation starter.

BTW, a friend of mine ended up marrying my brother.

Sorry to tell you, but this is impossible. You cannot see someone staring at you when you are not looking. If you weren't looking, you could not see her staring. So maybe you are staring and she looks at you because she is creeped out that you are staring.

If you are interested in her, go talk to her. You know, have a conversation. If you are in university, then I think it is time you grow up and actually learn to converse with someone, so give it a whirl.

I agree with the others - you have more than ample conversation starters. How about your friend? Do you think he would introduce you to his sister or would that be harder?

Just wondering == what would an anonymous text message do for you? She wouldn't know who you were so more than likely she would delete it -- as it could be some weird creep.