^Obviously she got to know Richard and formed an opinion on him after he and Sharon were reunited.
My thought is that someone being your friend's dad or even your mother's boyfriend is one thing, and having someone be your stepfather and in your house all the time and in a position of authority of you is quite another. I believe Dawn also mentioned that she and Mary Anne were so focused on the "sisters" part they forgot the "stepparents" part.
"You may not believe this, but I was good at acting evil."--Karen Brewer