Alcoholic mum - coping mechanisms?

Hi, I'm new to this forum but really feel I have reached the point where I just don't know where else to turn to. I'm 24 and my mum has been an alcoholic now for the best part of 10 years, maybe more. I have a younger brother and sister, my brother is 12 and my sister who is 10 has a number of health problems, struggles walking and has sever adhd, meaning as amazing as she is (and she really is the most amazing little girl) she is more than a handful to look after, and i know my mum has struggled with this as my stepdad has always worked long hours, weekends included. My mum struggles with depression and binge drinking and it only takes something little to send her into another cycle of drinking. I live at home so I am always here to look after my brother and sister and make sure they arent aware of what's going on, but I just really don't know what to do anymore. I feel like I can't make plans or have a life of any sort and I'm also in my final year of uni my studies are taking the brunt of it as well. My mum has been to a private rehab before and NA meetings, but she doesnt seem to make the effort anymore and the episodes are just getting worse and more often to the point of her soiling herself and also driving around under the influence. i just can't take anymore and I don't know what to do. I try and take the car key and her purse but she ends up guilt tripping me and promising things will change and i just dont have the energy anymore to put up a fight. My stepdad is just as lost for what to do and we're just falling apart as a family at the minute. My mum is the best most loving person and mum ever when she's sober but i don't even know the person she becomes when she is drunk. I haven't told my dad, who im otherwise really close to, because i know my mum would be mortified, but it's just eating me up inside. i feel like I just want to run away, something I would never do for the sake of my brother and sister, but I just have this suffocating crushing feeling in my chest constantly and i don't know what to do. if anyone has any advice or ideas at all I'd be so grateful to hear.