It's implied that is the case, as the novel later on reveals that Penelope tried to run away a few times but they just built more walls and filled holes she found so that she won't escape, she can only go to events she is invited for, they talk a lot about wanting her gone, but they don't actually let her leave while abusing her and acting like it's her fault, maybe they don't want to see her running away because her absence would remind them of Yvonne or some crap like that, but the fact they abuse her while refusing to let her leave just makes them come across as total jerks.