EDIT - MISTAKE IN TITLE, HIS MUM, NOT HIS MIL
Long story short, MIL has fallen out with her daughter who she used to spend a lot of time with.
Since then, she's been spending a lot of time with DH, meeting up with him and suchlike but she also rings him several times a day. She's newly retired and sadly lost her husband two years ago
This Christmas I am hosting for my family, there are 12 of us and I am cooking a big dinner. MIL is 100% welcome to come if she wants to and this has been made clear to her. She also has two other sons and their families she could go to, and also probably her daughter still
Instead of taking up any of these options, she's asked DH to come out for lunch with her, just the two of them and he's said yes.
DH doesn't understand what my problem is, he says he's still spending Christmas morning with us and is only popping out for a couple of hours then coming back. I can't understand why he would choose to go and hang out with his mother for 2 hours at Christmas instead of eating the food I've cooked at home with his wife and two children and his in-laws, with whom he gets on very well, and why he's just run straight there when she's crooked her finger instead of telling her to stop being silly and go eat with someone or stay on her own if she doesn't want to.
I should add - as this is important - the entire family are all going round to hers on boxing day and having a Christmas dinner then too, so she still gets to see everyone. We tend to alternate between in-laws and she hosted Christmas day last year and we all went.
AIBU? Should I just suck it up? Or would you be upset?