i believe there are some tell sign to why u were asking this, just go with the flow man, you cant stop her if she wants to. I would say continue to trust her unless u saw something that is concrete enough for you to confront her. Count it as a blessing that it is still in a bf/gf relationship.
it is going to be very depressing to continue thinking this way. all in all, talk is easy for me, i still hope you can overcome it.