Why did her behavior change?

I'm guessing she didn't want to jump into anything. FMfatale made a point about her wanting to make sure everything was safe too. Probably another good reason. She changed her behavior because she probably wants to see what you are really like. You can only tell so much about a person online. Giving you her number was a big step, she obviously wants to talk with you more. You can tell a lot about a person by how they talk on the phone. She seems to just want to get to know you better.

It's hard to say without generalizing. But if I were to hazard a guess, I would think that her original attitude was likely out of self-protection. You never really know what sort of people you're going to meet online, and you don't want to give too much of yourself until/unless you're sure it's worth (and safe) taking to the next level.

She probably genuinely wasn't interested in meeting anyone in person - and that's not something you'd want to publicize even if you were. But life can surprise you, and somewhere along the line, you two probably developed some kind of connection that changed her mind. I'd take it as a good thing - she finds you interesting and trustworthy enough to actually want to meet you. Two weeks is a bit quick, but it's all very subjective. The choice to meet at a local restaurant is smart - it's neutral territory. Public place, not personal for either of you. She's checking all the right boxes.

So if you find her as interesting as she seems to find you, then go have a nice lunch. I've actually made a couple incredible friendships which began online - not something I generally do either, and I'd still say as a rule I don't intend on meeting online contacts. But it happens.