Younger sister is an alcoholic

Not sure where to start to I’ll just get right into it. My (33f) little sister (32f) has been an alcoholic for several years, starting when she was about 15. She lives at home with my parents along with her 6 year old son who has several learning disabilities. She admits she’s an alcoholic and just laughs it off like it’s not a big deal. She has a fiancé who has two children as well, 14 & 12. They have been together for 6 years and do not live together. Anyways, whenever I go to my parents house she is drinking, averaging 10-12 tall boys of beer a day. She somehow functions enough to get to work 4-5 days a week. My parents drive her as she has never had her license. We butt heads a lot when she drinks but in general we are pretty close when she is sober. My issue right now is that she gets extremely hateful towards me when she’s drunk. Example: I was at my parents last night and my dad and I were trying to watch a movie, her son and my son (also 6) were goofing off so I asked several times for them to go into another room. My sister was passing out on the couch but then also started goofing off with them so I said for them again to go in another room. She absolutely flipped on me and accused me of bullying her son because I supposedly was only telling him to be quiet which was not true at all. She then tells her son to stay away from me and told him I don’t like him and I’m a fking b*ch.

That was a mild night. My parents have called the cops on her before for going after my mom who has MS.

I’m not sure if I need advice or just an ear but it is completely out of control. She isn’t like this every time but it happens often enough. I’m more concerned about her son who misses several months of school a year because she won’t get up in time and he already has issues to begin with. My parents would kick her out if it wasn’t for him and she refuses rehab. Thanks in advance for any advice.