I disagree. Just pretending that MarbleMac never happened would have been a far greater disservice to her.

Big Mac and Sugar Belle finding happiness meant inflicting pain on Marble Pie. And that's just how Love and Life works, happiness for one means depriving happiness from another, sometime.

PS: If you want to know what really screwing over a character looks like, just remember what Kim Possible did to Zita Flores. She was Ron Stoppable's girlfriend right up until they decided to ship Kim and Ron together. Zita suddenly disappeared from the show with no explanation, and they carried on as if she never existed…