You can only try from your end and deal with your own desires. I had a good friend of 20+ years that started pulling away, I only think I know some of the reasons (since we never talked about it) but they are "her" and that's the best I can do for myself; other people have their reasons/non-reasons and that's them and that has to be respected.

Call her and make a specific date and/or if it doesn't work out, you have to move on?