Okay so backstory is I have a friend, I wouldn't call her a close friend but we used to meet up for coffee sometimes and now facetime once a week or so. I also know her mother quite well (this is relevant) as our parents used to be friends and I went round to friends house a lot when we were teenagers.
Friends mum is very very paranoid about covid- she doesn't have any health conditions but is at more risk due to her age. Basically doesn't leave her house anymore apart from to go for walks.
Friend hasn't seen her mum face to face since August- and that was outside at a distance. They had planned to spend Christmas Day together (not in tier 4 so allowed) providing friend basically self isolates for the 2 weeks prior. She works from home so easy enough to do.
Here's the dilemma- friend has basically told me when we facetimed that she's not self isolating, has met up with different people, been going to restarants, out shopping in London, etc. She said she was planning to pretend she had to her mum, and basically what she didn't know wouldn't hurt her.
I was talking to my DP and she thinks I should message her mum on facebook, so at least she knows and can choose not to see her if she's not okay with that. I feel like I should keep my beak out because it's not my buisness and I don't want to interfere.