It’s a blended family. I can’t stand her, ever since she disavowed Trump after the election. Matt was begging Trump to give her a job in the press secretary’s office. He finally did and then this is how she repaid him, by jumping off the ship with the other rats.
I know nothing about a blended family but I did hear Mercedes say this and was very disappointed. IMO, it came from a place of weakness—too chicken to stand up for him. I think she’s said positive things since then but her character had been exposed.