Does she really not notice I'm there? Why does she ignore me?

It definately sounds like she's playing games. As I'm sure you know, women are a mysterious creature. Maybe she likes you and she's just confused and not ready for her feelings. Or maybe she just knows you like her and she's throwing you little tidbits of attention to string you along to feel good about herself. In the end, I'll say it's down to instincts. Listen to your heart, what does it say?