What should have happened is that Deanna, having told Michael that she couldn't be a good whatever and simply live together, would then move in with her aunt until the big day. Said unseen aunt would be able to provide us with a bit of insight into what was eating Mira that she was so caught up in the process that she'd missed the point; instead of April telling her that Dee and Mike were living in Toronto, not Sin, we'd have Mystery Aunt trying her damnedest to get Mira to meet her daughter halfway instead of messing up by trying to have the wedding she wanted by proxy.
We could also avoid making Mike look like a clueless dick who can't understand why anyone would take anyone else's feelings into consideration. After all, Deanna is at least trying on some level to make Mira happy and thinks that she's doing so. Lynn probably didn't intend it that way but she makes it clear that Mike cannot even begin to understand that anyone who isn't him deserves that consideration; if a thing conflicts with his needs, the idiotic sociopath thinks that he's being enslaved.