Well Phones are there not to raise attraction but to set date! Just talk the obvious,how are you bla bla bla.... but deep conve needs to be held in person. The only way to increase someone's appeal is in person.  Make an effort to present yourself well, strike up a conversation with her, and then ask her out. She is not responding to your texts maybe its  because she is getting  tired of you; she sees you in class nearly every day, and you are constantly online to respond to her messages. Be courageous and make an approach. Having said that, I don't genuinely advise you to engage in any kind of sexual activity with a classmate.  If something goes wrong, it would be strange to see that person every day l,and lets face it,most relationships dont work in campus. Choose wisely. Sincerely ThatDude