End of a Friendship?

Ive been best freinds with this girl for nearly 7 years now, and shes always been bubbly, easy going, the group joker kind of girl, but over the past year she's changed a lot.

She turned into someone who was always moody, always bitching about our other friends to me behind their backs, and if i dared to disagree with her shed turn on me, so i would just shut up and listen to her.

I thought this change in behaviour might be down to the stress of living at home. Shes always had troubles at home with her dad, so much so that she moved out about three months ago. For a brief period after that she seemed back to her old self. It seemed like everything had sorted itself out and we were all back to normal.

But over the past couple of weeks shes turned into this completely different person when she's round me. Shes negative about absolutly everything, and whatever mood im in after ten minutes of being with her i feel like crap because thats the effect shes beginning to have.

When in groups she's fine, nothings wrong, but when we'r alone she constantly bitches about people she knows im really close too. I cant talk to my other friends about this issue because they only see the happy side of her personality.

I really dont know what to do, we used to be such good friends and i dont want too lose that, although i feel i already am.

I want too, and know i should really talk to her about this, but in a way im scared, and i wouldnt know how to go about it.

I just wanted to hear a few other opinions

I guess just be there for her when she needs you it sounds definiatly problems are home are contributing to her being moody, right her a letter maybe telling how concerned you are.