Am I at fault because I cared for my MIL when her own daughter would not and she now blames me for everything wrong in her life??!

MY sil had gotten POA of her mother, at which time she helped herself to my MIL's money! My mil started to go down hill with dementia/stroke it was progressing very fast. She was also a fall risk and had had several. One was while she was in the care of my sil, she took her mom to see the Dr. and my mil fell right there!!! My sil didn't even try to break her fall!!! Her whole face was shattered, broke her nose,her cheeks etc.!! I took care of my mother (with help from my siblings) who was a large woman, if she would have started to fall "I MOST CERTIANLY WOULD TRY TO CATCH HER" wouldn't anyone!!?? This is just one of many ODD senarios we observed while the sil was "in charge".? When the money started to run out so did she. She decided that it was to much for her to handle so she handed it to her older brother, whom was never contacted on any of the legalalities until he got the paper saying she was "Giving " him POA! This woman took her own mothers money and assets and squandered nearly all of it, leaving her mom with nothing!! Her son (my husband) is taking care of all her needs now. To top it off the sister is now moving out of state!? There has never been any love lost between her and I, she isn't my cup of tea in a person. This I discoverd before my marriage to her brother so my eyes were always open to her treachery, unlike her family members I seem to be the only one who saw her for the viper she is! Well my husband is aware now and can't believe what is going on. This person always blames others for her actions and is quite an accomplished liar, she really thinks she has done no wrong!? I just need to see what can be done besides going to our lawyer. If there is anything that we can do? I have kept quite for 30 years with this person all the while she was injecting her venom into all those who would listen to her lies......but I've been slandered enough and retaliated with an email to her! She profesess that she is a "Born again Christian" but you can't tell beause she dosen't practice it! I am not much of a church goer but I don't have to bombard someone with profanity to get my meaning across. How can your own flesh an blood do this to their own mother????? I lost my Mom,Grandma and a brother in the last 2 years so I am no stanger to anger and grief at this kind of loss. But my MIL is still here.... and her ONLY daughter dosen't care enough about her to helpout!! Only thing she did finish was to help herself to her mom's money!!!