SIL playing "pick me" at Christmas

[PerspicaciaTick]

DH and I both have tiny families so Christmas Day this year is going to be at our house. DH's 80yo widowed Mum, my 80yo Mum and Dad who both have massive health issues, DH's brother and his wife plus us and our 2 children.
All fine. Except SIL has announced she will only come if my Mum isn't there.
Talk about playing silly buggers and upsetting everyone. In what world am I going to withdraw a Christmas invite to my parents? Why didn't she just make an excuse and decline the offer? Now we have hurt feelings, zero explanation from SIL, and a nasty atmosphere.
I'm really wishing she'd just said "Thanks, but no thanks" instead of playing stupid pick me games - AIBU?

As hard as it is, I'd try to keep it really light and breezy. A simple these are our plans, it's a shame you won't make it but look forward to seeing you and yours in the new year.
Don't acknowledge her weird as fck response. Seems she's looking for a barney. It's none of your business what she thinks so let it go. You'll leave her hanging on to nothing. Plus she's done you a favour, she sounds like a stupid dckhead!

Op has not had any contact with the SIL these are "messages passed on".

Then probably wise to drop sil a text directly

Hi Meredith ,

I hear you, I was the host for many years for DHs family. MIL was very much one for everyone being together and I went along with it for far too long. Several years we would discuss everyone contributing but they always had an excuse. It took me being in hospital over Christmas to break the cycle.
I really regret that I missed time with my own siblings and parents because of this( we lived closer to DHs family), and I still resent it even though MIL is long gone. I would recommend you make this year your last to host if you can, and tell them in January - and mean it !

If you want to get some more perspectives maybe open a new thread? This thread is about a slightly different issue and some posters may not see your post.