Gosh, what a shock, eh?!

When I've been put on this sort of spot, I just simply say "Sorry, It's just not my thing" and leave it at that.

This must be so awkward for you, things like this really change how you see a person you've known for years. It can make one yearn for the days of just not knowing about this. And you scratch your head thinking "Why would she think I'd be into this sort of thing?"