There are a number of animal products that can be used in wine making. Isinglass (from fish swim bladder) is one, used as a clearing agent IIRC.

Not All Sugar Is Vegan. Surprise!
And here's the bone-chilling truth...
There are a number of animal products that can be used in wine making. Isinglass (from fish swim bladder) is one, used as a clearing agent IIRC.
Yep, as mentioned above; Also, I think gelatin can sometimes be used to fine wine, as well as casein or egg white.
I should add the same case can be with beers. Some have lactose in them for added sweetness (see milk stouts), as lactose doesn’t ferment well and contributes residual sugars. They can also be fined with isinglass – Guinness at least used to fine their beer with isinglass, but I feel I’ve heard that they’ve changed their process some time in the last ten years to make their beers vegan. Ah, a Google search says that since 2018 they’ve been vegan.
Weird. And someone up thread mentioned vegan sugar. Sugar? Vegan sugar??? Huh???
Some vegans will eat those things, others won’t.
If I’m cooking for vegetarians, i look for cheese with vegetable rennet.
It appears the issue is animal-derived products being used in the production process to some degree.
Which makes me wonder about the logical underpinnings of all this.
I’ll speculate that the gross weight of insects killed in harvesting what becomes a pound of white sugar is probably much greater than the weight of whatever animal products might be used in the treatment & refining of the same pound of sugar.
if “by-catch” is a problem when harvesting tuna, it ought to be when harvesting e.g. sugar cane.
if “by-catch” is a problem when harvesting tuna, it ought to be when harvesting e.g. sugar cane.
Is there a fruit or vegetable that is harvested with no collateral damage?
No. Which is exactly my point. Some of these heartfelt bright line distinctions are drawn in places that don’t actually stand up to rigorous scrutiny.
My vote for “least bad but still shitty option” would be to invite neither nephew nor wife and inform him privately of why. And publicly make sure he knows and is tangibly shown that he’s fully loved and appreciated in other ways that don’t involve family dinners at my house.
Has anyone given her direct feedback that she’s making the holiday unpleasant for folks?
If not, that would seem like an appropriate and adult first step, as opposed to jumping to uninviting family from a family holiday.
Also, to the OP, while I totally get that there are vegans and folks out there who have diets of choice that can become sanctimonious and rude, there’s also an element of rudeness and sanctimoniousness in a response of “we don’t eat potatoes without butter in this house because it’s just BETTER and TRADITION!” She’s a member of the family now. She needs to adjust to participate with the group, but so too could the family adjust to its new member. Instead of making her her own after-thought dishes that no one else will eat, maybe there are one or two vegan dishes the whole family can share in the spirit of family and community.
It’s tough when no one will eat the food you’re eating because it’s perceived as lesser, especially when you’re one at a table of many.
I mentioned what it is upthread: bone char. Bone char is sometimes used to make the sugar whiter.

And here's the bone-chilling truth...
For example, sticking with major brands, some Domino sugar is vegan. Some is not. It depends on which refinery they come from, as some still use bone char in their filtration and bleaching process. Lot numbers beginning with 1 & 4 are vegan; lot numbers beginning with 5 are not (according to the most recent information I could find from last year.)
It’s tough when no one will eat the food you’re eating because it’s perceived as lesser, especially when you’re one at a table of many.
That’s a good point. If vegetarians/kosher guests bring their own veggie burgers, to cook on foil at the BBQ, i don’t try to make it food for all. But when i have vegans, etc., To dinner, i try to serve some vegan dishes that everyone will like, i don’t relegated them to their own inferior food.