My mom made my brother and I both power of attorney, etc...and she had a codicil written into the will that said it had to be divided evenly and if either of us contested the will or tried to get more in court, that person forfeited his rights to everything and it all went to the other. Smart woman, my mother. My dad has me as executor because he knows that my brother can't be trusted with it and I can. I think part of my brother's problem is that we grew up poor. We lived below the poverty line...all my clothes were hand-me-downs from friends, and his we all from thrift shops because he was so big there was no one to hand clothes down to him. Mom had worked at a savings and loan before she married my dad and she was excellent with money...very frugal. So while we bought generic EVERYTHING in bulk, with coupons and on sale, we always had enough but never high end stuff. Mom had grown up during WWII and rationing, so she was used to saving things and reusing things....old coffee cans became ovens, tuna cans became candles, milk cartons held grease drippings, meat trays were saved for christmas cookie platters for friends, newspapers became shelf liners. So I think my brother figured that since we grew up with nothing, it was time he was entitled to the things he wanted and had never had. So as soon as he got a paycheck, he went and bought a stereo, or a this or a that. And he got used to doing that. So when he got to college and had an apartment, he didn't think about things like rent, or gas, or electricity. As soon as he got money, he went and bought the next toy. He nearly ruined his best friend/roommate's credit, not paying the bills that were in his name, and he's the one who finally went to my mom and told her she needed to do something because he couldn't bail him out anymore and he was suffering for it. That's when my dad bailed him out. I think he was just so tired of never having the things he thought everyone else had, because we grew up in a rich town where everyone else had money.
Your mom's still alive, isn't she? Do you think your sister will be more mature now? I was only 25 when my mom died, my brother was 26...so we were just young. But I don't think he'd be any better today at 40 than when he was 26. He still hasn't learned his lesson and I kind of doubt he ever will.