What should i do about my bestfriend? she has been a little unfriendly lately?

Me and my best friend, have been best friend's for 3 years.Until recently, She has started getting proper jealous if i speak to my other friends, this has made our relationship strained. I have grown closer to another friend because of her jealous acts. She has started ignoring me for long periods of time, if i even speak to this person, or sit next to her at lunch time. She writes status after status about me on Facebook, so blatant she may as well tag me in them. I have also been getting vicious formspring questions asked towards me (may be her). However on the other hand, she has become very clingy, always sending me messages, even when i'm not online e.g. 'you there?' 'your ignoring me arent ya' 'why are you ignoring me' i dont know whats wrong, its becoming a little creepy. Help ?