Mrs. Tiflin is a mystery. Or maybe there's just not much to her. It's kind of hard to make the call, to be perfectly honest.
She seems to support her husband's decisions when it comes to running the ranch, and she doesn't question him. And when it comes to parenting Jody, she takes a backseat to the men of the house—Carl and Billy. She's there to nurture and make the meals. In other words, she seems like your standard homemaker.
The one place in the novella where she seems to take a stand occurs when her father visits, and Carl starts to make fun of the guy while he's out of the room:
Mrs. Tiflin turned on him. "Don't do that, Carl! Please don't!" There was more of threat than of request in her tone. And the threat irritated Carl. (4.129)
It's awesome that she's attempting to defend her father from her husband's offensive remarks, but the sad part is, it's this threat that sets Carl off on his rant. You know, the one that Grandfather overhears? So yeah, her attempt to defend the guy actually winds up fueling Carl's mean streak.
And any backbone she seemed to have in that moment disappears entirely just a few lines later when Grandfather enters the scene. Instead of standing up for her dear old dad or trying to explain the situation, she just sits there silently, barely breathing while Carl digs himself deeper and deeper into the most awkward hole that's ever existed in conversation.
What's clear to Shmoop is that this is not a lady who takes charge of a lot of situations. She runs a good house, cooks good food, takes care of Jody when he needs it, and that's enough to be getting along with, thank you very much.