I sympathize but I have to put in my two cents as I was that person who took advantage. My dad was a great dad but he liked to manipulate people and I learned how to do it really!!! well. My dad's side of the family have an attitude I inherited. Do what you want before doing what you should do. I still fight this as I am a big procrastinator but I do understand how someone like your sister could do what she is doing. I had a very!! large inheritance from my grandfather in my father's place as he had passed away.
I bought a van and gave my kids all money and used it to do whatever we wanted. We never had money to do anything when my kids were growing up. My husband had an excellent job but I was always making bad decisions money wise and doing things we couldn't afford.
So you get in the mind frame that I can't make it go far enough so I might as well do something that makes me feel good instead. I was always behind in payments and relied on my dad to get me out of trouble a lot!!
My husband's favorite saying was "We can't afford it but we're doing anyway!"
Then my dad died. I no longer had him to bail me out of jams! My mom does help me and she actually helped me straighten myself out eventually and now I pay my bills on time and am an honest responsible adult but it took me until I was 45 to see the light and get on the right road.
It is easy to tell yourself that you want it and I am going to have it no matter what!! It is a little like being an alcholic. This attitude is so ingrained that it is hard to change. Like quitting smoking it is a matter of rethinking how you act each and every day.
I still have to consciously choose not to do things that I would have done before. I choose not to misuse my money. But it isn't easy!
I never held myself accountable to anyone!! Not even my husband. I would do what ever I wanted no matter the cost.
So please don't judge her too harshly. Not everyone has the skills to be responsible. It takes time to grow up and understand there are better ways to live.
Noone could or can now tell me how to act or do anything!! You can not live her life for her. She has to be accountable for her own actions. You are not. I know it is hard to sit back and watch destructive behavior but there is not much you can do.
I hope you can find a way to let her go her own way. It is best for you if you can. In time I hope she will see that her behavior is self destructive but if she doesn't I am sure she still cares about you all. '
I do have to say tho that money is not my first priority my family is. Money may come and go but your loved ones are more important than any amount of money!! I hope the best for you and your family!! God Bless you and keep you!