Oh god this is so sad. Just because she's your mum you DONT owe her. If anything, judging by what you've written, it's her that owes you.
Just bite the bullet and say you unfortunately haven't got time to do her hair for a while (you could pretend you'll do it when your schedule calms down). If she kicks off, I would be inclined to remind her just how she's treated you over the years. You sound like you'll be well rid of this toxic relationship. I'm extremely lucky to have the most amazing mum but my hubby's mum is crap and after years of trying to get along you sometimes need to face up to the fact that they will always be selfish and nasty.
Just bite the bullet and say you unfortunately haven't got time to do her hair for a while (you could pretend you'll do it when your schedule calms down). If she kicks off, I would be inclined to remind her just how she's treated you over the years. You sound like you'll be well rid of this toxic relationship. I'm extremely lucky to have the most amazing mum but my hubby's mum is crap and after years of trying to get along you sometimes need to face up to the fact that they will always be selfish and nasty.