I feel like I am in this exact situation with my boyfriend. At the moment, everything feels stale. We never do anything together and it almost feels like we've lost interest.

I spoke to my therapist about it and the best advice she gave me was talk about it. No matter how uncomfortable or how awkward it may seem, it's worth it. The way my therapist explained to me was - you can't fight alone for a relationship with another person. You'll end up exhausted and give up because you have no help and it's impossible to take on all that responsibility for another person.

Whichever way your talk goes with her, you'll have some idea of where the other person is at and what can be done from there.
Good luck