Sometimes people like that need a swift kick in the ass. I don't know what you've been telling her so far, but next time she tried the "poor me, I can't do it" act, tell her she's pathetic and useless. Tell her she's not going to change anything if she just sits around whining and feeling sorry for herself. Tell her she has the choice to stay the way she is and be miserable, or to try and be something great. She'll probably get really pissed off when you say this, and either she will use it to fuel the change she so desperately needs, or she will continue to make excuses and feel sorry for herself. Unfortunately you can't control how she feels, but you can choose whether or not you want to continue a relationship with a person who is an emotional anchor. If she contributes nothing to the friendship and is always negative and drags you down, cut her loose.