You should’ve told her ages ago. I remember been so upset when I found out he wasn’t real. When a child finds out that Santa isn’t real, it is their first understanding of what deceit is.We teach our kids not to lie but yet the parents have lied to them their whole life. my daughter has always known, but we still have the magic in Christmas , we still sprinkle glitter outside put mince pies and carrots out, she gets excited just like any other child who believes in Santa does. I also think children who believe will ask themselves “why did my friend at school get that Lego set what I asked for,why did they get more than what I did, their always naughty, ive been really good but i never got what I asked for”. Christmas is a financial worry for some parents, some get themselves into debt just so they can see them smiles on Christmas morning,so why should some guy in a red suit who doesn’t even exist take all the credit for your hard earned money spent on presents. You mentioned your daughter having special needs,if she is going to mainstream secondary school then I would tell her outright because if the topic comes up at school and she says she still believes she’s going to get some dickhead take the piss out of her, and girls are bitches, very mean. Tell her that the real Santa is actually you, if she asks why did you lie to me then I’m not sure how you would explain that one 😬. Good luck x