Maybe the girl really doesn't want to pursue a relationship. That would be my best guess. Also, being too insistant is a turn off. Next time, send the girl a text message, and don't do anything else for a week. Then send another text or email. If you don't hear anything back, she's not interested.
When you do get an answer from her, here are some tips:
-Don't assume she's looking for a serious relationship. She may just want to be friends, and thats ok because friendships usually last longer than dating relationships.
-Don't talk about yourself when you're together or communicating on the phone. No girl likes a guy who only knows how to talk about himself. It just confirms what many women think: Men are self-centered. This is probably not the case, but talking about your life and your interests only will give her that impression.
-Ask her about her life-not interrogation style, but casually, and then REALLY LISTEN! Reflect back to her what you've heard and how you think she might be feeling.
-Do nice things for her without expecting anything in return. Any girl would be impressed with a guy who offers to wash her car or help her in some other way.
-Enjoy your time with her-be yourself and find lots of common interests that you can talk about.
-Don't talk about your ex girlfriends or exwife.
-Be a gentleman. Those are in high demand these days.
Hope this is helpful, coming from a girl/lady with a wonderful husband who follows all the above advice!