Ostensibly, the only reason she was there was she was a hot model.
When someone is in the business of selling themselves and their sexuality, someone else taking a crass photo of pretending to grab said persons breasts doesn't seem as egregious as other circumstances. I can easily see it having been a running gag, or something similar during the tour.
Again, this isn't meant to be in the context of "therefor she deserved it" - it's meant to be in the context of how adults on a tour might be expected to interact with one another, based on who they are and what they are there for.
Was it a funny picture ? Not to me as it is, not with no other context. And Franken would probably only dig himself deeper trying to explain one.
Let me also clarify this was about the picture - that we can all see and agree on. The kiss was wrong if it happened they way tweeden described it. But franken does seem to disagree it happened that way. And her political background, which I also posted, gives reason for pause on taking her story at face value with no questioning motives.