So my friend SUDDENLY decided to NOT take contact with me anymore. It has been like this for a week?

She's really just this irritating, selfish person that I don't get why I even bother hanging out with anymore, and I'm the one with the reasons for that as well! Now, out of the blue, she won't talk properly to me. I've called, and tried to talk to her on Facebook, but now she's only talking to our other common friend, and not me. She has also declined my suggestions to do something together, so of course I won't be the one to start a conversation again! She just seem uninterested and will not be the one to talk to me. Yeah, she's that harsh and selfish. Now what the heck should I do? I want to be friends with her again, but that's really hard of course when our conversations always ends with her being all difficult and sarcastic as a way to show her power over me, who is bad at defending myself and discussing. I don't even have anything to defend, she just has this attitude when we talk!