As far as her farther allegedly molesting her, that's simply not the least bit believable. Nothing she says is believable because she's a compulsive liar and a manipulative sociopath. Probably a bit delusional too.
Everything she told the cops during her interrogation was a lie. There was no Xanny the Nanny, unless she was referring to Xanax. She made up several other fictional people too during her story.
She even offered to take the cops to her job at Universal Studios. So, much to her surprise, they took her up on her offer. She pretended to be leading them to her office, that it turns out, didn't even exist. She was simply lying to the cops (and her parents, among others) about even having a job.
And I think it's obvious that she was a spoiled brat who is a compulsive liar because her parents always let her get away with lying all the time with no consequences. Even after she skipped her last half year of high school to hang out partying with her boyfriend she would just lie her way out of it when her parents asked about the truancy notices, and they would believe her. And even when they did find out about it, even though they knew she didn't graduate because she skipped a half year of school, they still threw her a huge graduation party.
I think it's a combination of spoiled brat selfish syndrome and perhaps also the onset of schizophrenia.
A combination of nature and nurture.