I’ve had a similar problem before – sometimes even if you get along really well with someone, it’s difficult to think of what to say in the beginning. If I’m talking to someone just for the sake of communication, I usually tell them about what I’m doing or thinking (in a conversational way), or I ask them those questions, and expand on the conversation from there. If she’s saying “nothing, you?” it’s going to be a lot more difficult, and for that I’m sorry.
I’m trying to think of an example, though… it’s pretty normal for you to want to know her hobbies/interests, so a little interrogation is ok. Once you have a foundation, though… build off of it. For instance, a guy I liked really loved movies, and he’d seen tons of them… I like films as well, so whenever I watched one I’d text him to ask if he’d seen it, then we’d talk about it… our favorite parts… or I’d tell him about it if he hadn’t seen it, then see what he was up to… and so on. Music is easy to relate to as well… find out what her favorite song is at the moment, then tell her when you hear it on the radio, you know? That sort of thing. The more you get to know her, the more connections you will have to another, and the more you’ll have to talk about.
I hope that helped.