My mother’s last lipstick mark is on a cup I cannot wash

Dear Delyara, My mother drank tea in my kitchen the afternoon before she died unexpectedly. The cup remained beside the sink after the ambulance, hospital, relatives, everything. There is a faded red lipstick mark on the rim. Mum wore the same shade for forty years. I have washed every other dish. Not this one. At first, nobody noticed. Then my daughter offered to clean the kitchen and I nearly shouted when she touched it. I explained. She put it back without saying anything. It has been six weeks. Dust is beginning to settle inside. The tea stain at the bottom has dried dark brown. I know this is unhygienic. I know lipstick is not my mother. Yet washing that cup feels like participating in her disappearance. Today, I bought a display box online. I hate myself a little for that. My mother would call it ridiculous and wash the cup herself. Maybe that is what I am waiting for: enough time to hear her voice teasing me louder than the fear that water will take one final trace of her mouth.