The girl that I can literally text back and forth for hours is the same girl that I still get nervous talking to at school. Most of our in school conversation are very brief and are almost the same like "Hi how are you"? How do I overcome this fear and break out into better conversation in person?
Approach her differently. Stay away from boring conversation topics like "How's it going" and instead ask her interesting questions. Think about what you talk about during text and bump that up. If you guys talk about her going somewhere, bring that up in person and ask her more about it. Become good at being aware of the things she talks about and turn those events into conversation points.