The fact that she's being paid to be there makes it all the worse. If it's, say, at a bus-stop or in a shop then she can reasonably turn around and say "Get your hands off me, you ****". In this situation, she's essentially powerless to do anything at all at the time.
I voted option 2. Even though I think it's really not okay to do that, I think it's worth noting that Sagan is relatively young, lives a pretty sheltered lifestyle and has got where he is because of his legs, not his head. The way we talk about him sometimes, it's no wonder the guy acts like he's not in the real world once in a while.
It reminds me of something the often offensive and occasionally incredibly perceptive comic Frankie Boyle said about Cristiano Ronaldo: "Of course he lacks perspective. He's been treated like he's better than everyone else since the age of about 8 simply for having incredibly well-coordinated feet. It's a wonder he hasn't killed someone."
Yes, it's inappropriate, but people are a product of the societies they are in. In Peter Sagan's world he's treated like royalty, he probably has quite a lot of success with women when he's not groping them in public and he also, by winning lots of bike races, ends up spending a lot of time around podium girls who are treated like pieces of meat, not good for anything but looking pretty.
I think that's the real issue that this has raised. Why are we so surprised that, when we maintain a tradition like having podium that looks at those girls as nothing but objects, someone ends up treating them like objects? In my opinion, podium girls don't really belong in the 21st century, and when things like this happen the culture that tolerates them is more to blame than the individual.
Back to the individual in question, it's worth noting that he almost certainly didn't mean any harm. The fact that a guy can do that and think it's harmless fun is, in my view, a problem with society, but Peter Sagan is not to blame for all of society's ills, no matter how silly you think he finish-line celebrations can be.