Cluster B shit (personality disorders, for those not into psych babble) is weird. It's very hard to figure out why someone develops these disorders, but it definitely seems to be both nature and nurture. BPD seems to be at least a little bit genetically heritable, although it's hard to parce out when the parent also has BPD and treats the kid like shit.
Suffice to say that there are a lot of BPD cases with seemingly no "event" that causes them. Sure, some BPD chicks (mostly chicks) get raped as kids or whatever, but there's seemingly equal numbers who had cushy, easy lives with their biggest trauma being a death of a grandparent or something most people get through OK at their age.
I think there's a likelihood that Jessica's Mom and Daddio have some seriously fucked genes that they passed to her. Her Mom might have done all sorts of drugs while pregnant (a lot of BPD Mothers do this).
And as others noted, it's really hard to figure out if these folks truly were abused because they are lying liars who lie.