I would honestly recommend talking to her one on one, don't tell her you aren't interested in her anymore, but tell her that you want to have more depth in conversations and what not. It's normally for people to hit that rut, just dont immediately call it off, it could be something that changes. 

I've broken up with an ex for this same reason and not a day goes by that I dont think back and ask myself if it would have been better if I would have just said something.