The Miami episodes of Jersey Shore premiered on MTV just one week after the cast began filming again in Seaside Heights, so what we're witnessing now on this season are their raw reactions to reliving painful moments from the past.
On last night's episode, it appeared that Sammi was just being a bitch toward Ronnie for no reason—since illogical bitchiness is what we've sorta come to expect from her—drudging up shit from months ago when they were in Miami. However, the cast moved into the Seaside Heights house around July 22. The Miami season premiered on July 29, and judging from the time lines on their various Twitter accounts, they were permitted to view those episodes. So it would make sense that around this time, Sam was finally witnessing what she'd only read about (in an "anonymous" letter): Ronnie's promiscuous night out in Miami, ending with him cuddling in with Sam in her bed. On the After Show, Ron admitted that while he had eventually fessed up to some of his blunders to Sam (off camera), he had been so wasted that night that even he didn't remember exactly how much of a dick he had been.