>>80305742>She never had to learn to respect her brother and his ambitionWatch the ending of Weirdmageddon 2 again. >I appreciate what you said back there, but if you want to take Ford's apprenticeship, I won't get in your way.
She actually did accept that, because ultimately she cares more for Dipper's happiness. Dipper was the one who decided against it, since HE realized he didn't want to grow up without her.
Dipper and Mabel are literally so close they don't want to grow up apart. The reason they cling to each other like this might be because the Pines parents are neglectful, if not outright abusive. There's a bit of evidence in the show that points to this, but that's a whole other can of worms.