Well, that turned all wholesome and happy by the end. I think Dave morphed into another person. The real Dave would have pretended to be okay after hearing that secret and then kept his daughter at arm's length.

The mom (Jean, I think) to her kids, Molly and Michael:

 

"I tried to talk to Dave about [Heather] before you all came home, but he said I wasn't trying. He said I didn't love her enough."

Okay, why did Jean and Dave get married? Not only is Dave doing nothing to help his obviously troubled 7-year-old daughter ("shrinks mess up your head" or something), he's a terrible husband as well.

"'You know, though, Molly, that Dave and I count on you and Michael to take care of Heather. It's up to you to make sure she doesn't run wild in the woods all day.'"

OMG, I hate these parents. The mom seems to know that Heather hates everyone in the family except Dave, her dad, so she must know that all of Heather's claims about how mean Molly and Michael are to her are lies. And she still makes the bulk of the work involved in watching out for Heather Molly and Michael's responsibility. If something happens to Heather, you know they're going to blame the 12- and 10-year old they told to watch the 7-year old, instead of thinking "Hey, maybe us adults could have switched off between working on our art and actually watching out for our kids."

I already dislike the little sister, Heather, and the parents. I realize that Heather has some issues and her father is doing absolutely nothing to help her through them, but she's a brat. And I dislike that Molly and Michael's mom let them think they were going to do the enrichment program and Science Club over the summer and then just uprooted the family without warning. She made it even worse by lying to them about how isolated their new home would be. Would it have hurt to let the kids know they were house hunting? Or did she and her new husband seriously just buy a place out of the blue, without thinking about anything except "we can do our art here"?

I decided to go with a library book I've had checked out for a while.

"Once I made the mistake of letting her play with my old Barbie dolls, the ones I was saving for my children"

Uh. The narrator is 12. Did any of you ever start saving stuff for your future children at that age? Because I certainly didn't. I mean, I don't know that I've ever wanted children, but it seems weird for a 12-year-old to already be planning for them.