What she also doesn't realize is that Elly doesn't take kindly to having to deal with the problem she created and wants very much to be avenged. Just as she's teaching Mike to make the mental association between his cool uncle Phil and the pointless torment of trumpet lessons, what she's doing in this arc is making the kids believe that when her parents show up, she doubles up on the discipline to not only prove to the old bat that yes, she did learn to be a good mother from her but also to drive a wedge in between Mike, Liz, April and her parents so that they don't somehow team up to destroy her.
The sad part is that she's two thirds of being a success. The Mike who called Jim crazy doesn't know sweet dick all about Jim and assumes that Marian's greatness begins and ends with being a better cook and more indulgent caregiver while Liz could barely stand to visit the old boy when he was sick. The reason that April loved the old coot is that Elly was too busy being a big shot to turn them against one another.