Dirty Dancing is a movie about Baby's relationship with two men: Johnny Castle and her dad. Her mom doesn't factor into any of these. It's not that they don't dislike each other; they just don't have much in common. Marjorie's more like Lisa than Baby.
However, we must give Mom credit for one line (out of, like, four total in the whole movie). At the very end, when Johnny removes Baby from the corner, her Dad stands up to stop Johnny. Mom puts a pin in that real fast.
MARJORIE: Sit down, Jake.
Perhaps Mom's remembering a key event from her own past. Whatever the reason, Mom knows that Baby's big dance is going to be a pivotal moment in her young adulthood, and she won't let anyone stop it. Maybe mother does know best.