My sister is manipulative user, my mom in denial and enabling, my mom lies about all the using, my sister is a con artist. What can I do?

I'm from a big family, 8 of 9 siblings are college grads, in good relationships, great friends with one another, all successful, happy and independent. The other sib, has never had a real job, gone thru a few marriages, lost a few homes to foreclosure, has NO long term friends, and has pattern of going from one person (typically older people or men)to another, taking them for all she can then accusing them of abuse once they tell her "no more" and dropping them. She has stolen money from a few of her sibs, lied about us (she told my family that I kept asking her young children "where's your daddy?" when she had served him with a restraining order, she claims to not be invited in family things like baptisms or xmas even though we always included her so our parents would be happy, cried to parents that siblings were attacking her when they ask her really simple normal questions), she is also an alcoholic. Typically gets slurry drunk and has recently just started passing out in the evenings, sometimes waking up and starting to undress in front of the little cousins or cussing and attacking people. She is pushy and beliigerent when she doesn't get her way and can say truly cruel things ("Mom hates you. She told me she can't stand when you come here.") She also pushes my mom around and makes her buy so much junk(sis's a hoarder) and has completely filled my mom's barn, yard, and home with stuff my mom buys. She typically has lived off my parents, either in property they own, in their home, or with their funds. My father who could somewhat keep her in line recently passed away and as we all predicted, she and her kids have moved into my mom's nice house. The first thing she did was empty out all of my dad's closets to make more room (and probably to cause drama). She didn't tell any of us. Mom had told us all that she wasn't removing anything for a year, but when faced with this she changed her story and said she was so happy that sis did it. Mom herself is child of alcholics and wants peace at all costs. She pays all sisters bills, phone, gas, mechanics, food, electricity, cash, booze, gives her the nicer car and is stuck at home for days at a time when sister leaves, and watches, feeds, and puts the kids to bed almost every single day. The sad thing is Mom is such an enabler she lies to our face about it, acts like she wanted to do that, or said it just happened once, etc... although we have all seen the pattern for the last 3 decades. On top of it all, my sister does nothing to help my mom. She sits in the big home like it is her own or visits her rich elderly friends as my mom works the 5 acres and takes care of her kids. All the rest of us live a few hours away and come out to help as much as we can (before she moved in there was someone there at least twice a month for long weekends). My husband will not kick my 76 year old mother out of her bed, the other bedrooms are "off limits", not to mention my sister's drinking and her declaration that guns are on the property (bad combo with crazy drunks), so we have had to severely limit our time there with our kids (even though we all LOVE their grandma and her house). We recently went and stayed in hotel to come help, we had heard my mom was working non-stop in the yard, and watching the kids non-stop (not from my mother she would never admit that), so we went and worked like dogs helping my mother, while sister sat in the house, entertained old people (probably rich or vulnerable), and left her kids with mom. And my mom covered for her! In rare moments of exhaustion or frustration my mom will admit that sister has drinking problem and personality issues and that she is pushy and harsh, but she is stuck because she wants to protect the children. Then she will never mention that again and try to downplay it if we bring it up, saying how great sister is. Mom's totally getting used, running a welfare state for completely entitled manipulative immature irresponsible sister and our mom lashes out at us if we try to say anything about it. I asked her to my son's bday party and she said she couldn't be away from the farm that long because she is the only one that does the work (rare moment of honesty- altho she didn't also admit she has to babysit sister's kids 24/7) when i suggested that sister could have a work list for those days, mom lashed out at me and said it wasn't the work, mom wanted to have a social life and she couldn't just go back and forth out of town all the time-totally random thing to say, I was inviting her to one weekend bday party, sister takes her car for days, leaves her kids for day, takes all her money so she is broke.I know she lashes out at me because I won't lash back like sister and she can't admit truth. I'm so SAD. I've done this so long I need to accept this is Mom's choice and I can't protect her. Mom is healthy, activ, mental ok- exhausted, depressed and frazzled trying to keep cover story up. I LOVE my mom so much.