If you're shy about having confrontational talks, I suggest being subtle about it. You could tell her that you recently bumped into an ex. She how she reacts. It's always hard to know how they feel, if they aren't obvious about it. This is why I won't date shy men. They hold their feelings in. Or you could save yourself all of this questioning, and phone her or text her. Emailing her, gives her a chance to leave it and come back
to it later. I suggest not using e-mail for closer communication. You're far better off phoning her. You could tell her that you feel as if she isn't into you anymore. If she asks why, tell her what you told us.