We've finished dating, but on the friends issue...?

I think you should probably give it a few weeks so she can cool down a bit and feel less embarred about the way she ended it with you. If you bump into her don't try to force conversation, but smile, say hello, ask her how she is blablabla. Like I've said, don't try to force friendship with her. If you just phone her up out of the blue she'll feel like she has to say hello to you and you don't really want that, you want her to speak to you because she wants to, not because she has to. Sounds like you're being a good sport about it anyhoo, so you'll probably end up being friends again. Just don't stress so soon.