How to get past two decades of anger/hurt

Please bare with me... This story could be made into a book/movie. And I'm sure there are plenty of extra details I could add. Here goes...

Between 1995 - 1997 my aunt went completely off the rails - leaving her wonderful, family orientated husband for a man off the internet who is a disgusting individual (think going from Patrick Swayze to Danny Devito).

She ran up huge bills and they almost lost the family home. My grandparents bailed them out... And off she went with the new boyfriend, getting black listed from rental after rental, ripping off Centrelink... Basically leaving a trail of destruction in their wake.

Her youngest child ended up a pregnant teen, middle child went off the rails and is a compulsive liar and her eldest (who had always been the apple of her eye) became a recluse - keeping to himself and stuck with his dad (thankfully, as he is the only one who has turned out well).

My grandparents were both horrified at her behaviour as she had always been very family orientated. Shortly after all of it went down, my grandmother died of a heart attack - the day after she had been on the phone in tears to my mum saying things like, her daughter would end up in jail, etc. if she continued the life she was living and still is living.

After my grandmother died, there were a few years where we heard nothing much about or from the aunt and then... my grandfather started to get dementia. He was walking in the middle of the night into random rooms and waking up not knowing where he was, couldn't count basic money and had been an engineer, etc. The aunt found out and decided this was her opportunity to move in.

My grandparents were very wealthy people and had a lot saved + brand new car in retirement (which ended up with a blown up motor after being about 5 years old), 2 houses (one beachfront and one large acreage), etc. She started moving others on to his main property and had foster children there and all sorts of random people living there. At one point there was about 15 people living in his house that we know of... There could have been more. I have no idea why the Department of Child Safety would have allowed what she was doing. We believe she ended up losing her blue card indefinitely.

Anyway... She was going on yearly cruises - but none of the household residents were working... And eventually my grandfather's money dwindled away to nothing. He had $2 in his account when it went to court.

I had been pushing my mum to contact the Adult Guardian and she had, but the process was lengthy. It eventually went to 'court' and the aunt was found guilty of financially abusing him.

The next stage of court was about to proceed - the physical abuse and the fact that she had fraudulently made him create wills and power of attorney documents while he had dementia... When he died.

My mum decided to let her go and see what she would do... And of course, the aunt being who she is, sold all of his property and spent everything. She has lied to her children saying the reason she left their father was because she caught my mum and him in bed together and that my mum wanted and got all of my grandfather's money. The truth is my mum got absolutely nothing and wanted nothing from him, except to see him looked after properly.

These days the aunt is long gone out of our lives. We don't have to see her or deal with her again. But I am carrying so much hatred towards her. Hatred because I blame her for my grandmother's death, for financially and physically abusing my grandfather, destroying two of my cousins lives as children, the defamation towards my mother which is 100% not true, ripping off the system - when everyone else has to work hard for people like her to live a life of luxury doing nothing to contribute, etc.

How do I get over 20 years of anger? That's 2/3 of my life. When this started I was a child, I had no control to stop what happened to my grandparents who I loved and adored and my mum was too placid/timid to do anything about it. I've spoken to a pyschologist about this and it hasn't helped at all. I'm angry that the aunt has got away with everything that has happened. I guess sharing this helps get it off my chest, thank you to anyone who reads this whole thing... Hopefully it makes sense.