Fight Club
So this movie definitely leaves the viewer with a lot of questions and I read a few things, notably as to why
she got pulled by her feet on the floor and such things.
Well, if you remember the film Fight Club, Edward Norton's character was persuaded of the existence of Brad Pitt's, and everyone understood that it was his own doing, explained in the film by sleep deprivation, and probably on a deeper level, some rejection of a perfeclty labeled life in the kind of society we live in.
But in The House on Pine Street, the paranormal element eclipsed that for a lot of people I guess.
If it was all paranormal, then fine, the "ghost" did it all, and killed the husband, and the kid could see someone and talked about "there are ghosts in the house" because only 'sensitive' and 'innocent' souls would be receptive to that kind of manifestations.
If it was all in her head, as she would have been able to believe she was pulled by her feet or develop enough strength to vertically break a door (well, a thin and old one), and maybe, fought her husband enough to push him through the window, then, she could also have believed that a little kid, who didn't articulate well, was uttering such words/ sentences; easy to imagine what you want from baby talk.
And then of course, it could have been a mix of both, or something else; I'm not trying to write an essay on the movie, so that's it for me on the subject :)