This is the mental illness known as narcissistic personality disorder. https://www.mayoclinic.org/diseases-conditions/narcissistic-personality-disorder/symptoms-causes/syc-20366662 I believe this is often caused by a falling away from or rejection of one’s upbringing and faith tradition. Anecdotally, my observance of this disorder in others seems to be accompanied with some sort of minor relational trauma that is never dealt with by the parents involved, or they don’t recognize the seriousness of the problem at the time, and eventually spirals out of control for the individual (usually young women).
I’m not a psychologist, but you may want to seek such professional help to find a way to intervene on her behalf.