What was blanch doing?

Once the party gets started all the kids walk in on the granny Blanch watching a porno, but what was going on off-screen that was so awesome or funny? They even took a picture that was supposed to be hilarious.

Am I missing something? Was she masturbating, receiving oral, or what? If it was just a picture of an old lady sitting on a bed looking at something then it wouldn't be so cool to all of them ... but the camera didn't give any indicators as to any of those things.

Am I just dense? Any clues?