1) DO NOT try to build rapport through the phone. Even if she wants to, leave it for when you two are together. Do not let her know of your hobbies, interests etc. Let the air of mystery build in her own mind. If she wants to message, either turn it flirty, change the topic or plan a means of getting you two spending time together. Less tele-communicative contact is best. Don't be afraid to draw everything out and keep her chasing. If she has any interest in you, she will chase.
2) Ask her out as soon as possible. Her IL is probably at the highest point at the moment and if you can pick it out whether she is interested or not or if you are up for the challenge, do it. You have to make your intentions clear. No, nice guy beating around the bush.
3) Kino, go in for the kiss or get her into bed. In doing so, you let her do the reasoning as to why she is with you not you chasing her. From my observations of my friends, it's those guys who have done this that have bled out a healthy relationship with said girl rather than spending eons chatting and doing nothing and only to realise she has gone back to her ex or someone more exciting.
4) Don't take whatever she says seriously. Words and actions are two different things. She can be aloof messaging but treat you like a crazed fan when she sees you or she can sound like the sweetest chick in messages but treat you like a rock if you bump into her.
Good luck my friend. Learn from my mistakes and make the most of your opportunities!