What should I do about my friend? She never wants to come out?

So I have this 1 friend, and everytime we ask her to come out with us she gives a billion excuses. It's like pulling teeth to get her to actually come out. I know shes a little insecure about her appearance, but I always do her hair for her, and lend her my clothes to go out. She herself never acutally wants to go shopping to get her own clothes, and ALWAYS uses the excuse she has nothing to wear..

Then she'll ask a million questions about going out, like whos there, where it is, ect and then will say something negative about each aspect of that.

She'll keep this going for at least an hour, (making us wait around on her), before she acutally decides if she'll come or not.

But then when we finally give up and decide that we're going either way, she seems all upset and like "Oh well okay, I would've went but I guess there's no time now".

Like what is her deal? We do so much to try and make her come, and she either makes us wait forever on her, or gets upset if we go without.

I'm sick of always trying to appease someone who doesn't seem to even like doing stuff with us.

Advice? What should I do !