What do I do with my sister?

[Sarah]

Me and my sister live in the same house and she is very stuck up and only talks to me the most when she wants something from me. I do a lot for her and I am always helping her out and giving her money. We go days without even saying a word to each other and our rooms are right next to each other. I try to talk to her but she acts like she doesn't want to talk at all and that her friends are more important to her (she's on facebook and twitter a lot). Some days we talk but only say a few words and other days we go days without even talking to each other. Should I just ignore her and stop trying to talk to her? What would you do if this was your sister? She's 24.