The reason that I make what I wish to Hell was a joke is that for some ungodly reason that probably has to do with a delusional old fool simpering about how when she was eleven years old, she KNEW what love was and who she was in love with, Lynn is obsessed with the idea of pairing the children off at the age of eleven. As howtheduck tells us, this has a lot to do with why Deanna and Janice had to take a powder after next year's Halloween party of her getting a bug up her ass because Mike did something stupid. As he saw it, the idiotic plot would have had ten year old Mike torn between two extremes. On the one hand, we'd have Deanna as a stand-in for the sort of girl Lynn thinks twelve-year old Aaron should have gravitated towards and Janice as a living warning not to associate with the wrong sort. It's like how she'd later revive Deanna as a means to the end of telling him "I told you so" about the end of his marriage.
That being said, it's probably for the best that Ruth Johnston managed to convince Lynn that she should hold off on that until Mike was in high school so that she didn't get angry letters about kids growing up too fast. The letters didn't make sense to Lynn because of that whole "I KNEW I was in love, real love" at eleven thing she has.