One thing that could turn out to be true is Cassie's mother began to treat her worse after the protagonist left (can't say for sure about exactly but it seems to be about a decade, perhaps a bit more), which made her leave and led her to end up in that police cell (and to her surprise find out who was in the other one next to her). He does mention during his dinner with Ashe that he was left to take care of Guppy while their mother worked and in a Halloween picture the protagonist was looking at, Peyton (Cassie's friend) was drinking body shots from her and he sarcastically says their mother was a contender for Mother of the Year and he really didn't got along with her much to begin with, calling her a cold person. She even didn't like him talking to Cassie after he left, that he'd put ideas into her head or something like that. Perhaps in the next update it might be revealed why Cassie ended up there and give a little family background, and whether he'll be finally forgiven by her for going away so many years ago. That one could be a touchy moment.
It almost makes me wonder if the mother's personality will depend on the one we've set up for our MC. The mother being cold and not wanting MC to interact with Cassie could be indicative of some real fucked up possessive abusive mother shit, for example she gets jealous of Cassie 'stealing' MC's attention, things like that.
On the other hand, if MC is a dark personality.. that behavior suddenly makes perfect rational sense; the mother's frightened and disturbed by MC and is concerned for Cassie, but of course our dark MC is oblivious and views this as perhaps his first taste of the world punishing
him rather than the problem being himself, like any typical narcissist.
Of course, whatever Neon decides will be interesting! Could just be that the way we shape our MC is one of multiple interesting outcomes that an abusive mother could produce in her son. One who is particularly sensitive to the cruelty in the world, having experienced it from his own mother, and therefore one who is motivated to oppose that; or one who was 'born in the darkness' and absorbed all the twistedness only so he could take his turn and export his own brand of it. Or, you know, one who didn't inherit the psychopathy gene vs one who did, however you prefer to look at it.