Based on how we recall and interpret events, our opinions will differ greatly here.
I saw the whole thing with her parents as where her mother placates and encourages the FMC to allow herself to be controlled and abused, while the dad is both mentally and physically abusive. The mother takes the father's side, which just adds to the whole toxic situation. So of course the daughter moves far away from them. It doesn't matter if the child was a brat or not. Abuse through anger and gaslighting is not discipline not guidance. I've just seen this kind of scenario and variations of it play out negatively like this for others and myself in multiple times in my life. I've also seen it usually play out positively whenever the ones with authority and maturity act with empathy rather than anger and unfairness.
She doesn't make a lot of money because she is just drifting through life. She doesn't have any goals nor ambition as she has no self-esteem, so she does just the minimum for what she needs or wants, which isn't a lot with her mindset. I might be remembering incorrectly, but I remember the manga stating she doesn't have more dates because she keeps denying them and chooses to only go with the guy after she catches feelings for him; the agency still shoves people her way, but she is just refusing all of them except for the guy.
Yes, part of her defense mechanism is to upset others, but the separation with the guy at the end was different. She specifically desired to have him (as one of the late chapters says) unlike all her other relationships that were more just tolerated because they were thrust onto her and required no effort on her part to keep the relationship alive (the girlfriends and aunt). She is normally selfish, but with him she decided to let him go for his own sake rather than keeping him to make her feel better. The other people didn't make her feel better. He did. Normally with her cruise controlling through her current life, she'd just let it be. Whatever is easiest to deal with. On paper, her actions at the end appear similar to previous interactions with people, but the motives and how she left them is different. For example, she pushes her "friend" to help the guy, essentially hoping to pair the lady up with the guy the lady has always admired and having the guy with someone that would make happy. She didn't just burn everything to the ground and leave like she normally does. She actually took the effort to resolve things for the better. Old her would have made sure to hurt that lady at the end rather than helping the lady and the guy.