I think it's more likely that she was asleep and he was doing it as a joke. I don't think this photo proves anything, but rather how you interpret it depends on their prior context.

See 2:42 into this skit. If it were those two people in the picture they would both have found it funny. If Franken and Tweeden had a good relationship, and had just spent several weeks making bawdy jokes with each other on tour, this might be nothing.

The problem is that he seemed to think it was OK at the time, and now she's saying it wasn't. Has she changed her tune? Maybe. Did he mis-read their relationship? Looks that way. Did he really grope her during a "rehearsal"? That's the he said / she said that we'll never know for sure.