I don't think the writing for Abby has *ever* worked even with more charismatic actresses in the role so count me in the camp of those who are not bothered by MO herself: she is inoffensive enough and do not quite understand the fixation on HER.
Write Abby out to join Ashley wherever she is; that, I would get.
But recasting? Problem with Abby isn't MO. They need to retool the character first and then they can think over whether MO can pull off the new version.
Isn't the point of a reality show to show real life. Karen made have good one liners and her fashion has improved...but her name fits her.
Wouldn't it be better for the cast to not attend...and conflict springs from that?