Sadly, Elly is just that sort of jerk. We're destined to get a minty-fresh reminder of her belief that she has to shut Michael up lest HER reputation take a hit in a year and a half when the Enjos move into what used to be Connie's house. As we'll see again, Elly went out of her way to keep Michael from saying anything about Keith and Dawn's appearance because she was obviously convinced that that something would be an ethnic slur. The really telling part of all of this is that Michael's managing to blurt out that the only thing he noticed was that Brian was his age did not reassure Elly in the least. Not for her the comforting revelation that Mike isn't the bigot she thought he was; she's too busy being upset that he made her worry about nothing.
One must also take into consideration the other reason that she's at pains to control his vocabulary: her fear that if a bad thing happens just once, it'll keep on happening. Since she needs to feel as if she's a helpless victim of selfish people who just don't care about her to feel good about herself, the idea that her children aren't trying to destroy her out of malice is not one she wants to see. She has to be an intolerant idiot letting her life slip away from her because that's all she knows; after all, she's spent so long trying to prove to her mother that she's a good girl, she won't allow herself to relax and admit that she has good kids because, well, Marian never did and her way is the only way that looks safe to follow.