To Tell SIL To Stop Claiming Things?

There's your answer. Just don't invite her. If not inviting her isn't an option ie Christmas then NO is your only word.

Can I have .. NO and repeat.

OP why is this your issue to deal with? Why aren't the two other people (your BIL and your DH) getting ahead of it and dealing with it instead?

I know, but it's mayhem in the shops and often difficult to get a turkey unless you've ordered it in advance. And they might be working today and tomorrow.

She would deserve such treatment, but if it were me I'd rather avoid something that drastic. It might cause a long-standing rift. I'd prefer the various other options that have been sugested. If they don't work this year, then don't invite her next year.

If this is real, Just keep saying:
Don't be daft
Don't be silly
Of course you can't
And repeat.

I would approach it collectively beforehand. Set up a group chat with her, Dh and BIL. Just say that you wanted to be clear that you're letting all leftovers to have over the rest of the Christmas period and no food will be leaving the house. If you can get your dh to send the message instead, so much the better since they're his family. Also add the same goes for presents.

Totally feel for you - I think you and DH should absolutely take a hard line - ‘no, you can’t have the left overs, I’m planning to make a casserole/bubble and squeak with them tomorrow’ and ‘No you can’t have our gifts and frankly, SIL, it’s rude to ask, so stop asking!’ Don’t engage beyond that but make your line in the sand very clear. Get your DH to do the same. You’ll only have to do ti a couple of times as she should stop - and if it embarrasses her or makes her feel uncomfortable, well tough, karma and all that.

And I’d not invite them next year - BiL needs to take responsibility for not reining her in.

BIL has asked us to leave it alone and just ignore her because she gets embarrassed

Maybe she should stop doing embarrassing things then?

Honestly, it's tedious but I think you need to vocally push back every time. "Um, no - obviously you can't take home my presents". "No you can't have the leftovers, we bought it so any leftovers are for our lunches". "If you like xyz so much, maybe you and BIL should treat yourselves to some, it came from abc". It will either stop her doing it or stop her coming!

You don't need to talk to her before hand or stress over it. Just call her out infront of everyone everytime she says anything. She tells people not to eat you say I made this food for everyone not just you if you want leftovers I suggest you buy and cook the food. As for the Christmas presents just say why would I give you my Christmas presents there mine you have your own

Have they ever invited you over? Just wonder what kind of hosts they are…

I hate stinginess more than anything. I would just keep replying with a cold ‘no’ this time and then never invite them again.

please update us…

This!

Print out a bill for everything she’s about to receive/consume on the day, tie it up
with ribbon and leave it next to her cracker.
Tell her you only take cash in advance.

Except this and many other suggestions, will make other guests feel awkward, too. Likewise discussing ones own plans for the leftovers will make everyone feel that they shouldn't eat too much.

I'd simply go with a text beforehand saying to make sure that they have food in for boxing day, as there won't be any leftovers going home with them.

The resent thing can simply be met by 'no' and a refusal to engage or give eye contact.

The fact is if she doesn't stop this bizarre behaviour, she can't come without someone being upset. Why should it be you, yet again, and in your own home at Christmas ffs? Will your DH back you up? The email upthread, giving her prewarning and the option not to come, was well worded. I'd try that and tell the others to put up or shut up.

me and DH are both in agreement that we need to say she can't behave like that because it makes everyone else awkward but BIL has asked us to leave it alone and just ignore her because she gets embarrassed
She doesn't behave like someone who gets embarrassed. She seems shameless.

SIL has the hide of a rhino and clearly wouldn't be bothered by not being there. BIL rightly gets embarrassed by her behaviour but the ball needs to be in his court. Either he attends family events solo, neither of them come or he makes it clear to her that he wants to go to things as a couple so she needs to behave. Whether she alters her behaviour is entirely down to her.

For all OP knows this may be a deliberate plan (alongside her attitude at the dinner) by SIL to get herself excluded from family events and she is hoping to provoke someone into banning her from events.

This should have been sorted out ages ago not 2 days before Christmas.

Let them come and deal with it ... that would be rude to give away a gift somebody has bothered to buy me.

Eat as much as you like folks, x is just teasing.
Do not give her leftovers to take ... tell her you have bought the food and what is left us going in the freezer.
Straight after Christmas your husband needs to tell his brother that you are having a smaller Christmas next year.

I like the 'don't complain, don't explain' method, every time she starts to ask for something, cut her off with a "no!" and carry on talking. The shot method is a brilliant one too though 🤣

BIL has asked us to leave it alone and just ignore her because she gets embarrassed.

She sounds openly shameless about her behaviour so how does she get embarrassed?

I think it is fine to say in advance that there won’t be any doggy bags and you are keeping all gifts - and frame it as if you’re giving themtime to get their own things

The BIL doesn’t want anyone to say anything as it embarrasses her??

I’d be going out of my way to embarrass her by highlighting her utter scrounging weirdness at every comment. “Why on earth do you say stuff like that?” “Why are you asking for my presents when I’m opening them?” “I didn’t make Christmas lunch so you could take it all home for yourself.” “What’s wrong with you? Why are you constantly asking to keep everything for yourself?”

I’d leave each remark hanging in the air too.

I'd also so that it's probably best to go down the road of making a more public comment then asking her to not say it in advance.
Oftentimes people need to be publicly shamed to change their behaviour so some of the comments that PP have suggested such as "don't be so silly, of course not" will work well.

I agree.

If you go out for a meal then say to the waiter she’ll be paying separately and make sure she hears!

At home just do a big laugh if she asks for something or say er No? And then laugh. I doubt she’d be more embarrassed she’s embarrassing already! Who cares

Ooo. Alternatively you could say. ‘Yes, of course you can have X for £££££££ but I’d need paying upfront!’ - joking not joking

We had a relative a bit like this, not as extreme as asking people not to eat food but definitely didn't want to pay for anything when out and it was totally joy sucking and miserable. Xmas is utterly miserable with her because she panics that she may spend something (certainly not gifts that's for sure).

This time as pp said whatever she says firmly counter it. I'd even say if she persists.. Your ruining my Christmas please stop.

Definitely do not invite her next time

You could try preempting her comments.

For example, when you sit down to eat say that everyone should tuck in, eat till their full but you have plans for the leftovers so no doggy bags this year.

When it comes to exchanging gifts say that you hope people enjoy the gifts specifically chosen for them and, if you’ve got children, remind them to say thank you.

I’d also prepare some responses:
We’re looking forward to seeing what we’ll make out of leftovers and have some ideas - bubble and squeak variations, turkey curry, a buffet with extras added.
As for gifts, lie if necessary and say what a thoughtful gift and gush how much you like it so her comments would sound rude.

Or, play her at her own game. Serve up and say don’t forget ‘Donna’ is expecting leftovers so don’t eat too much! And laugh. Say to her the same thing she says to you with each present she opens.

Or, take her to one side before the day and explain how it makes you feel when she does those things and then wait for her to respond. Don’t fill the silence.