I fully understand the heartache about this. Not only do you have the passing of your mom, but you believe it to be provoked by the hospital, so it wasn't under even halfway decent circumstances.
I am my mother's attorney in fact. She is 86. Already I have had to counter other siblings. Mom made me this for a reason. I do my best.
Please know that your mom is no longer suffering here...and to me, we all go when it's our time. That she waited for you to leave is so typical,and shows they are really in control at the final breath. My dad waited for my mom to whisper to him he could go.
Anger is a normal emotion at this time...but try not to let it overwhelm you. God is still in control, and though there were many other circumstances surrounding your mother's passing, HE determined when she'd had enough of this life.
Peace.