This is because every so often, we have to deal with the irrational and stupid fallacy "Holly wants to focus on something she can actually do something about therefore she can't care about something she can't be rationally expected to be able to do anything about" with the same sort of regularity that John makes hateful noise about problem hair. At one point, Holly flat out said that while she did actually worry about the big picture concerns that Val uses as a stick to beat her over the head with, there ain't much a middle school student can actually do so she'd rather focus on a problem she can solve instead of burning her life away because Mommy wants to heap too much on her.
This, as one could expect, meant less than nothing to Val because she doesn't see herself as she is any more than the Pattersons do. While Holly can be a pain in the ass who puts too much stock in clothes, make up and boys, she is right to state that Valerie does indeed expect far too much of her. This is something Val has in common with John because he doesn't realize that one of the reasons Liz was moody is that adults like him seem to be doing nothing to fix the problems he invokes because he assumes that it's not only her job to be an emotional crutch, it's on her to clean up his generation's mess right now so he can take credit for her hard work.