I have a feeling that a proportion of those stabbing thrusts were also directed at her mother. JMO
Snipped for space.
I think those stabbing thrusts are a life long list of resentments towards her mom, stepdad, and stepsis. She has been living with a family that she may have felt like an outsider her whole life, coupled with emotions from knowing her "real" dad had left the picture. Teenage years are emotional enough for the traditional family situation now add on the added stress of a broken/split family situation.
Also, IMO she not only premeditated the killing but was implicating the stepfather as the attacker (if the pictures posted upthread are of Dora and her father - IDK though and I should not assume). In one of the news articles (again posted upthread - not good at adding links, lucky I can post a quote and snip it) it was stated that she told police a mexican man was the intruder which made me think of her wanting to blame the stepdad. Which then made me think, wow how sad, she must have been mad at all of them her whole life.
All just my opinioin, and some of it based on the picture upthread, if that in fact is Dora with her dad.