My father passed away and my mother sold their house. My sister…

Thank you for your feedback.
I do not believe my sister has bullied my mother, however I have concerns that she may have manipulated/guilted my mom into thinking she owes her. A couple of months ago my mother told me she was going to give each of us $50,000 early inheritance and that she was going to give my sister $50,000 towards the mortgage which would be her living expense and on top of that, she would also get the $50,000 that the rest of us were going to get. When my sister put her house up for sale and found out she wasn't going to be able to list it for as much as she wanted, she told my mom she wanted more money from her. My mom refused and told her $50,000 was
Fair. (She was also given a $19000.00 life insurance policy that my parents had taken out on her when she was a child)
My sister has been renovating the house, buying new furniture and appliances and is also going to put a hot tub in. She has been spending on luxury items she does not have but has always wanted.
Today, I found out my mom is giving her $100,000 and can no longer afford to give the rest of us the $50,000, but instead will give us $15,000 including my sister who she will be living with.
I know that this sounds like I am after my moms money. This is not the case. I would prefer she hang onto it or put it into some type of investment for us later on. However, as she is disbursing money, I only think it should be shared evenly. I realize my mother is an adult and capable of making her own decisions, however I think it's outrageous that she should think it is going to cost that kind of money to live with my sister. She's convinced herself its fair. I don't see it. And I'm a little frustrated that my sister could accept such a deal.
Would you be able to provide some information or direct me to a resource on the costs associated with taking a parent in the home?