"You sure know how to talk back, young lady." Martha's lips twitched the moment she heard the way Anna talked to her. It may seem that she got annoyed at Anna, but it is not the case.
In other people's perception, it might seem that Anna was being rude to her just now, but that is what Martha wants from Anna and Aaron. Their firmness in the decisions that they are making. No matter what kind of decision they have made, they must always put be firm and be ready for whatever the consequences are.
Of course, Martha won't tolerate it if Anna talks back to her like that all the time. She might as well slap Anna's face is she does it again in a situation where she should have not done it.