I recently just started to notice how negative a good friend of mine really is , she complains about everything : Having a job and making money, being alive ( always saying she cant wait to be dead), She does not see the bright side in anything that happens in life, including waking up. I am her only friend because of her attitude I believe and because she claims she does not like people. She does not want to associate with anyone whatsoever. Honestly I liked her as a person, but all the pessimism that she brings is starting to make me not want to be around her. Should I distance myself from her or try to help her ? Thank you in advance :)

Part of helping her might actually be distancing yourself from her so that she learns people, including you, don't like being around negative people. I associate myself with positive people and people like being around me because I am a positive person. And let's face it, it takes too much energy to be negative. Distancing yourself from her would be doing yourself a favor, and I never mind doing myself a favor.

She has been a good friend by your own description, so I would sit her down and tell her that you are henceforth practicing tough love on her, because it's getting you down.
The minute she gets too negative for you, you are going to leave or hang up.
EASY!
No need for long explanations, or apologies, or soothing platitudes. One sentence. You could even say 'OK now let's go get coffee to see how this works.'

Let us know if you try this and how it goes!

"I am her only friend ... she claims she does not like people. She does not want to associate with anyone whatsoever."

Louise, I agree with you but only in part. A friend who doesn't like anyone but spends half her time complaining to her one friend is a manipulator. Basically she's lying. And that is as harmful to marisol as it is to the friend. The friend can get help herself. Marisol doesn't need to 'notify someone she knows,' nor does she need to say she's 'there for her.' Why do I say that? Because the friend holds a job, that's why. If she were so depressed that she is a danger to herself, she wouldn't be working.
Marisol has to look out for her own emotional well being first, and friendships second. She has already said that she doesn't want to be around the friend.

If you cannot honestly and openly express yourself to your friend, then you aren't really good friends and should limit you contacts with them accordingly.

Thank you Joypulv, This isn't something sudden I have tried to be there for her emotionally so she could feel like she had someone to talk to but its like talking to an emotionless brick wall and my attempts are always shot done.

If her being negative is effecting you, then you need to deal with it, I would be honest in any case, and when she starts being negative, tell her.