Well, first, she's completely fallen apart. Would anybody be surprised to wake up one morning and see a headline that says "Britney Spears Found Dead"? I certainly would not.
And while Jag is right, it's really not my fault. This all goes back on Brit's shoulders. Fame or no fame, this all comes back to being a simple human being, fallable like the rest: this stems from her cheating on JT. He was her inner peace, but she never realized it. It seemed petty at first to write that song about her, but now, it was the best revenge one could ever have gotten, and it destroyed her. Now it KILLS her to see him as the must have bachelor, being the main attraction at the Grammy's, back to back platinum albums and actually getting a tremendous amount of cred as a musician, actor and model. So when they were both single and he shot her down, then he and K-Fed were seen mocking her, she's over the edge now, perhaps no coming back either.
On a side note, I still think Natalie Portman was smoking hot with a shaved head. Brit, not so much.