Be strong and stick to your principles, doing so won't make you any less of a friend to this person, pampering to their needs won't help you or help them, just remain supportive but firm.
I know... she has all but cut off her best mate and worried her sufficiently during the first lockdown for her friend to drive down from Ruislip and come knocking on her door which she then refused to answer. She feel we aren't doing enough and when I sent her some links from the recent BBC Breakfast push to circulate mental health helplines, I got a retort of "I am NOT phoning them, I will just book myself into The Priory"...
Right now I am getting texts of "I don't know that I even want to go to Liverpool... do you want to come over on Christmas Day?" Shortly followed by "Oh I suppose you will prefer to see your family"
I have this darned commentary to do once I have had a fortifying cup of coffee. Will reply tonight when I am cooking my dinner.
ETA: My rellies in N London are on dad's side. He was a non-practicing muslim who drank, smoked, married a hindu and raised a CofE daughter (me) who then decided she was agnostic. My cousin and her husband don't really celebrate Xmas but they know I would be on my own over the river, and always invite me over and we do Christmas Mauritian-style, and I for one am very grateful that they offer every year.
I just broke my own rule and replied that I would have hoped her own family would understand what she's been through and that despite having grown up kids of their own, my cousins always have me over on Christmas Day so that I can spend the day with family. I also made the point that this year I can't even trek to the parents' graveside and stop off at my schoolfriend's parents place to say hi/stop for a cuppa as I can't risk contaminating their bubbles.
I think for the first time the real importance of bubbles (now... that's a sentence I never thought I would write as a trained journalist!) is becoming clear and even if BoJo and chums give us their Christmas leeway there is still some thought to be had about how to do this...!