What to do when she's playing hard to get?

I'm a 17 year old guy that just graduated high school. I'm interested in this junior, and I know she's interested in me, but she keeps playing hard to get with her texting games (texts me first but replies within 15mins to 3 hours). She's on her phone 85% of the time.. and whenever I say I gtg she replies within 2 mins or less. She always responds interested & tries to keep the conversation going but last night she just ignored my text back.. the conversation was going really well so I know I didn't do anything wrong. She's really worth it.. She's only been kissed once & never had a bf before but gets asked out ALOT & rejects them, but I've gone out with her before. What do I do now to keep her interested?