In all honesty I think it's hinting at something different. I think the orginal fl was like this from the beginning. The orginal fl is more resembling a sociopath that looks to constantly aid to Sera's suffering or give her reason to feel pain then claim she's the victim in every given scenario presented. Though it's only my speculation, and this doesn't excuse the previous Sera's actions in the slightest, it seems like she was being manipulated to some extent.
I don't think it was og sera fault completely for why the og fl hates our fl though. I'm definitely not saying og sera was a good person clearly she wasn't but I think the "friend"/og fl is one of those fake ass "friends" like that girl who is "friends" with fl in "marry my husband" (something like that" because if you remember the scene where sera was going crazy at a party before our girl was put into sera body and she was saying that the og fl was the one spreading rumors that's why she was breaking shit and throwing chairs and stuff and although she should have handled that better that doesn't change the fact that the "friend" was spreading rumors and damaging seras reputation and was
most likely trying to act like she was a saint trying to save the villain/beast. Also I think her smiling like a crazy bitch when Sera was attacked does indicate the girl isn't a good person especially when the brother who literally wants to kill sera and the fiancee who hates sera was more worried about her than the so called friend.
the spoilers will explain why og sera acted like that and why the og FL is really a villain
Honestly even if OG FL is a snake can you really blame her? In her eyes our MC is still the same person who tried to KILL her but she has to act nice and keep her reputation up even if it means being friends with the crazy bitch who tried to kill you. The OG Sera was a complete monster there’s no redeeming her, she tried to kill two people and someone is in a coma because of her. I’d be pissed if I had to keep my relations with such a person.