I sort of disagree with you. I do think that, if she wants to live by her own rules, she needs to move out. Period. I think that agrees with your points.
However, I think living with her parents doesn't necessarily mean not being an adult. As a member of the "I lived with my mom to help her pay bills after the divorce" club, I know that at times living with a parent can be a more grown up thing to do, even if it can stink. That said, while living with my mom I was also saving money and bought my own house so I could move out.
I voted that Abby's right. Because, as naturalT said, there wasn't a "sort of" option. Saying something to the effect of what CurlyGurly said above would have been a better answer, I think.