I work in private care. My boss and I have a great relationship. I care for her mother. Today her mother was ignoring me and I made a joke, one my boss has and I've made multiple times, about when she ignores me it's like talking to a wall. My boss heard me and told me I was completely out of line and told me to pack my stuff and leave. I obviously offended her and I'm not sure how to go about an apology.