Oh God. There is literally nothing good about Rebecca. Even avoiding her character traits, it doesn't seem like anyone even fucking cares about her. I mean, yeah, Larry was a jerk, but it was clear that Lilly loved and cared for him. Even Alvin feels like he's waiting for the opportunity to pop Rebecca in the mouth.
Based on their conversation, Alvin isn't the one doing the popping in that relationship. Also, I think they made Rebecca as unsympathetic as possible so that Clem's sassing her would be more acceptable. I mean, at the end of the day, Clem was blackmailing a pregnant lady. The only way that's not going to be perceived as a dick move is by making the target the most unlikable pregnant lady in the world.
You know, now that I think about it, it's kinda funny how the major jerks in this episode were all character archetypes that would normally have a sympathetic role in any other game. You had a young girl (Michelle), a friendly-looking dog (Sam), and a pregnant woman (Rebecca).
I do have a little but of sympathy for Rebecca, giving birth during the apocalypse is going to be an absolute bitch without modern medicine. They have Carlos, but that's it.
However, she brought it on herself by sleeping around. I mean, Lori had the excuse that she had every reason to believe that her husband was dead. Rebecca knew Alvin was alive and kicking.