Call and ask. Approach it as "I want to make sure I have foods you'd enjoy" rather than "I know you're picky, what is it that you CAN eat?"
Sometimes "picky" people just have issues with consistency, temperature, etc. or sensitivities to food. I don't have full-blown food allergies, but there are foods I avoid because I don't want to deal with the consequences. I'd be shocked if she wasn't used to people asking for more information. It'd be especially nice to have the information if this isn't the last time you'll ever eat with them.
I don't know what the rest of her "picky" eating is, but avoiding cheese and pasta isn't really "picky". Maybe she's allergic/sensitive to certain foods. I don't like pasta because it makes me feel incredibly full and gross after just a few bites and dairy in the afternoon/evening has me regretting my decision shortly after swallowing. Not all "picky" eaters are picky in the same way - it's not a catch-all - and without knowing more, you don't know if she has an allergy or sensitivity that prevents her from being able to eat everything she'd like.
I guess I really don't understand why one wouldn't call - what if you fix/purchase things and the only thing she can eat IS a burger?