Glad you are working it out.
I would never involve her in childcare of ANY sort again.
I don't believe for one minute her behaviour isn't deliberate.
You are a bit naive if you think otherwise.
Absolutely deliberate.
She was power tripping.
Take all her power away from her and tell her anytime she asks, "you are unreliable, not worth it".
25 years ago one of my friends wouldn't give her first child her mothers preferred name, her mothers name.
My friend didn't want her grandmothers name as she didn't like it, neither did her husband.
She had asked for an overnight for her friends wedding months in advance, to which her mother had agreed. Her baby was 6 months.
The first time her mother would have the baby on her own.
A week before she announced she was going away with her sister for a winter week, apparently had been booked last minute and paid for.
My friend was very upset and told her mother. It came out about her daughters name.
My friend couldn't believe it.
In that moment she just saw her mother so clearly.
She had no choice but to bring the baby with her and it changed her relationship with her mother forever.
She never asked her again for anything.
She pulled so far back from her.
Her mother had always been very controlling but she had never fully joined the dots.
Her mother offered many times to have her children subsequently but her offers were swatted away.
She did apologise about a year later but it didn't change my friends wariness with her mother.
That she would be so deliberately unkind to her.
Her nice father tried to intervene, but she never moved on her complete refusal.
Her lovely MIL became the grandparent that was their emergency number.
My friend said at the time the realisation that her mother could be so petty and deliberately unkind to her, triggered something deep within her from her own childhood, and she didn't want her closely involved with her children.
So she never did.
People who really care about you don't let you down easily.
It's a really unkind thing to do, and in situations like yours, I believe deliberate.
Never give her that power again.