OP, you should follow up and post the title of your book. I would definitely be interested in contributing to those royalties and it appears others in the comments would be too. Although there is one condition: you don't give her a cent of the royalties she's demanding. You worked hard and earned it, she didn't

Sucky shit some mum's say

I'm sorry OP. :( Your mom sounds like a narcissistic parent. She made the choice to have you, and her saying that you "owe" her for her decision is petty. Don't give her anything! She'll only demand more. :/

I think it makes a difference whether or not the child is still living at home and "freeloading." If the child is taking money from the mother on a regular basis, "but I just have to buy ____", I could understand the mother being upset about hidden income. Different story if she lives alone.

That's seriously messed up! Make her publish her own book. Otherwise congratulations on getting your book published! Let us know the title so we can all buy a copy!

She can't make you, so don't worry too much

Tell her you'll repay her when by sticking her in a retirement home

I thought parenting was free?

Did she read the book at least!!

I wonder if she's ever had a pet. 'I don't care if you are fluffy Mr Kibbles, you owe me a bunch of cash for this week's cat treats alone!' And of course children are a far bigger deal than pets.