Are you sure you were in law school at 18? Because that is terrible reasoning, and it's clearly terrible reasoning.

1.) The legal idea of being an adult has nothing to do with the maturity of the person, and that's clear if you've ever been to a regular college on any given Friday night. Nor is this a legal case, so it's totally tertiary to what you're arguing.

The maturity of the person is what's in question here: if the girl is logically immature (especially when it comes to her parents), then it would make sense for her to act irrationally. If she's not, it wouldn't make sense. But given the situation, it seems that she's not very aware of what her parents did to her before this last action. If you're going to argue that this girl was mature enough to act rationally, you have a lot of argument still to make. All you've done is implicitly posit such over and over.

2.) "Getting their parents' opinion on something" isn't what you're arguing here. Stay focused. You're arguing that the writer is at least partly to blame for her father being a shithead about her writing because she knows her fathers' personality. Again, this assumes she was acting totally rationally, and in the previous comment (to spell it out for you, since you seemingly didn't understand the implication, or you chose to ignore it; either way, you didn't meet that argument) I implied that probably isn't the case because most 18 year olds don't act very rationally, let alone when it comes to their parents, let alone when they're the child of parents like these.

Either way, in other threads people have shown you that the writer explicitly said she didn't want her father to edit or make judgment before he read the whole thing, and that's precisely what he did. Even though the act of sending him the novel is irrational if he has a pattern of this kind of abuse (and it seems that he does), she did make an effort to preemptively lessen her father's prickishness. She can't be blamed for her father's behavior when she specifically asked her father not to act like that.

3.) Speaking in generalities when trying to prove something as specific as this situation makes for an exceptionally inadequate argument because of the significant differences between what you've imagined and what the situation is. What law are/were you going into where they didn't teach you this? (Though maybe this brand of sophistry would convince a numb jury.)

Anyway, to answer your question, in this specific case, where-in the girl has shitty quasi-abusive parents and is probably looking for validation from them: probably not.