Welcome to Gaia! ::

... Well she wants to go vegetarian. She claims she's talked to her parents about it but they declined. So she wants me - the vegan - to make up a list to explain to her parents why going vegetarian will be good for her health.

And while I'm psyched she wants to go vegetarian, I've got to wonder if I should even help her battle.

First off, at lunch like five minutes after she asked me, she picked off a few pepperonis off another friend's pizza, which made me wonder if she really wants to go vegetarian.

Second is that she's really selfish and I don't even like her a whole lot, but I just can't dump her.
Like when she first discovered I was vegan a couple weeks ago, her initial response - you know, after the "really" - was "but that means you won't be able to go to my birthday party!"
Let me point out that her birthday is in December.

So do you think she's motivated and do you think I should help her out with this, or let her do it on her own?

I think you're right to be a bit skeptical. I think it would be good to help her a bit, but I don't think you should do all the work in case she's not really serious.

Instead I'd recommend telling her to do the research and find the reasons on her own. Explain that she'll find a lot of valuable information that way, she'll come across some recipes, and her argument will be more convincing to her parents since it's coming from her rather than from you.

If I were you I'd point her in the direction of this guild or of veg websites, maybe explain a few things to her, but that's probably about all I would do unless she shows more motivation.