I feel badly for your mother too. being in poor health and being subjected to screaming, ranting and raving. Your sister is very selfish in her actions.
I'm sure that part of the reason you stayed was to get the kids some rest and get a start in the morning if you are driving. I gather you have a baby and a 5 year old, so it's a process to get on the road, fed, bathed etc.
you can spend time with your mother separately in your own home where there is calmness later. You can choose not to serve alcohol too.