Maybe she just needs more time? Some times it can take people longer to realize their feelings.
I am not saying just sit there and wait forever...but I certainly wouldn't shun her. Just keep doing what you are doing. Has she recently been in a relationship? Where is she in her life right now? Still in school? Working? Maybe she just doesn't want a commitment right now...
It took almost 10 years a friendship for my SO and I to get together. It was a very long wait and both of us went through other relationships, jobs, school, etc...when we both became single at the same time, had finished out schooling, and were working in our careers, it just all clicked. 4 years in and things are pretty kick-ass.
Good things come to those who wait
