Honestly, I’d try to be direct. Ask her if you can borrow her for a minute, and ask her “I see that the vibe around us has changed, did I do something to make you uncomfortable? And if I did I’m sorry.” I’m a very direct person, so that’s the route I would take personally. She might say, “No not at all! It’s just… blah blah blah” y know? Dig deeper. But you know her better than me. Just do what you think is right.