So at some point, Staph's dad cheats on his wife for whatever reason. Fair to call that a shithead move, don't cheat, but I feel like that's rarely a simple situation and who knows what factors go into that that a 5y/o has no awareness of. If it was a shitty loveless marriage then maybe it WOULD have been healthier for her parents to split, but they stay together for her sake.
Literally ten years later, they get in a fight in public, likely due to Stapphy being a shithead teenager because let's be real, at 16 most people are shitheads. Whatever this probably inconsequential argument is about, Stapphy decides (in public, mind you) to escalate this to nuclear level by screeching about the most private embarrassing business her parents have. Her dad is apparently thoroughly mortified by this, is potentially SUICIDAL (ymmv whether that's performatively or not), and now the shit he said when he was so upset he was about to END HIS LIFE is Stapphy's gotcha about him being a meanie.
Life continues, teenage years suck because teenage years suck and her dad (who sounds apparently fucking mentally unwell during this period, though who gives a fuck, not Social Worker Stapphy) says a bunch of shit that is unfortunately not necessarily super uncommon from a certain age of adult in a certain sector of the country. Stapph does the most inconsequential pussy-ass methods of selfharm possible, because it's Serious You Guys.
Time passes, one would like to hope that they both grow and mature, and now her dad wants to try and do better (and seemingly succeed, since we have to dredge back to what also sound like the worst points of HIS life for traumaTM). Now Stapphy continues to freak the fuck out on him for everything, apparently blames him for being such a train wreck that getting fired makes her chug the hand sanitizer, etc etc.