I think singing is definitely a trigger sound for misophonia. I have never been diagnosed with it, but after reading this website I think I have had it for around 30 or so years. I’ve always had an aversion to irritating repetitive noises such as clicking pens, tapping fingers and feet and beeping, especially if they are unnecessary noises. These noises make me feel stressed and I’ve never known why until recently. In the last few years, because my husband is no longer able to work, he is at home most of the time. He does this fake opera singing which fills me with rage and annoys me so much. That’s what made me search online, to see if a noise can actually enrage a person. It’s been hard working at home during lockdown as I can hear him “singing” when I’m trying to work. Some of his other noises and now beginning to get on my nerves but that’s more cabin fever than anything else.
It is good to have a proper explanation for my feelings and I’ve asked him to read about it so that he can see why I get so annoyed with him.
With regards to how you deal with your mums singing, will telling her about misophonia help? You could also try distracting her when she starts singing, perhaps asking if she would like a drink or start chatting about something that interests her (tv, gardening, the neighbourhood gossip etc). She may be attention seeking (like my OH) and might stop singing so often if you spend more positive time together.