Mel because she was humiliated and cheated on. No one deserves that.
While Jason is accountable for his actions and he behaved VERY poorly for his part, I do think Fleiss took advantage of his insecurity and desperation. Jason should learn from this. They all should. You are a ratings number not a person to these people.
Molly did her part in being with Jason before the official break. I think she sold herself a little short with Jason and will have to make the most sacrifices. We will see in time if she thinks it's worth it.
Mel will get out of this the best. She's beloved by many. Jason and Molly need to wait it out and it will pass in a few weeks.