Maybe she believes that it's better to keep it to the family?As either a Land Lady or a Mother, Linda's actions aren't what you'd reference as being a "decent" individual, but taken as a Mother they are far worse than if taken as the Land Lady.
The prime example of this is the scene where Linda lifts up Sarah's skirt for the MC to perv on Sarah's ass. As a Land Lady, it's generally just pervy and not a nice action, but as a Mother, it's a fucking deplorable action to think, let alone carry out.