If your daughter is very upset, acknowledge her feelings - before doing anything else. You can say things like "I know you're really upset" or "I can see you're really mad at Mom." Her feelings are acceptable but her verbal behavior is not. When she has calmed down you can teach her that we never call people bad names and certainly not our parents! This information must be delivered in a "teaching moment" - a time when your daughter is calm and receptive. So don't try to tell her this while she is in tears or still very emotional. When she's entered that teaching moment, you can teach her that naming our feelings if fine (saying things like "I'm so mad!" or "I'm so frustrated with Mommy!") but name-calling is not. If she continues to have problems controlling her words, then you can eventually start to use discipline to help train her out of a habit that will not serve her well in life.