Twice, that I know of. First time, I come back from work to find 'porn hub' written in the google search bar. I was pretty sure it wasn't me (I've at least rebooted once since) so I checked the history. Sure enough, she was on there 20 minutes about an hour before I came home! Then the same today for 10 minutes (google schoolboy error again).
So, should I say anything? We've only watched porn a handful of times, never really thought she was into it. I think she'd be embarassed if I said anything and it might put her off. Honestly, I don't mind! It's a turn on what can I say. Dirty minx.