Widowed mother over anxious about family house party

[Unglamorousgranny]

Our mum has always suffered with anxiety and since our dad died in 2020 she's just getting worse & won't seek help. She over thinks things all day & gets things all out of proportion so much.
Anyway, my sister is having a house party tonight for family & friends. There's a small marquee in the garden, there will be some alcohol & a bit of music. Neighbours are aware of it & it's a one off special occasion, not a regular occurance. People who are going are sensible & not going to cause mayhem & be so drunk they're not standing. There will be a few little children there so everyone will behave appropriately.
She is going on about it all the time: do the neighbours know, don't upset the neighbours, don't drink too much, don't play music too loud,don't get drunk as I can't carry you to bed. We're all sensible middle aged & not selfish people who are going to be marauding through the garden, off our faces at 2am with the bass pumping so loud!
We have said things will be fine etc, she's building it into something its not going to be, we just want to enjoy a nice family & close friends party to celebrate a special occasion without any hassle. Asked her if she really wants to go, to which she has said yes, & have also offered to bring her back home if she's not happy. Have shut the conversation down for now, but she's sitting there looking all miserable while we're getting stuff ready. I think she'd rather we drank tea & whispered all night long so we don't upset the neighbourhood.
We sympathise a lot with her, do a lot for her & always there for her. She's probably miserable because she's worried about the party getting out of hand & missing our dad. But at the same time life has to go on & she's spoiling things today really. As much as we love her we don't think this is fair, & is a bit selfish of her, even though she can't help it.
What can we do? Insist she stays at home leaving her feeling lonely & unwanted? Or have her stay & spoil things with her going on if you dare have an alcoholic drink & worry the neighbours all night? She's also obsessed with recycling & will be hovering around everyone all night to make sure it's done properly, & it's not even her house.
She's not got dementia or anything, it's just the way she is.
Reading my post I sound unsympathetic, but I'm not. We love her to bits, but we just want her to sit down & chill, & let us enjoy our night in peace. Sorry this is such a long post, there was a lot to get off my chest!

[alexdgr8]

give her a task.
make a list of items that might be used which will generate re-cycling.
then at the event she can note down locations of said waste and later gather and bin.
compiling lists, making plans, can sometimes divert anxious people.
or ask her to keep a detailed log of attendees, their ages, relationships etc, as if she is compiling the society column.