AITAH for leaving my cheating fiance and then cutting financial support making her family go back to poverty

So I come here for advice because everyone on my family and friends circle thinks I'm overreacting and need to forgive and the usual bullshit so I want to know if you guys think the same...

Let me get you the context first I Paul (33m) meet my fiance Andrea (32f) in high-school both were (15) at the time of and since then we both stay together we had our rough patches when i went to study to a nearby city but used to visit her most of the time but when I finally got my studies done and was able to work at the town we both are things got better...

To this I have to add Andrea comes from a really poor family we talking 8 siblings a house made out of wood and a zinc roof gotta bless South America standars so knowing this I was mostly the provider of our relationship it didn't bother me I love to take her out to eat ice cream and see her smile same when I take her to car rides on my father car as time progressed the things I could afford got better since I study in IT and landed a high paying job working on the town Bank I was almost set for life I could say...

To this that I got myself a nice place to live that I rent from a old man that my parents knew we are talking one of those ranch houses with plenty of rooms to spare and 2 floors all so she could live on a bigger house like she used to say, then one day she ask me if her parents and 2 of her sisters (12f) and (14f) could come live with us that their living conditions are really bad and I knew that so I said yes we had rooms to spare and we weren't expecting a child so why not I thought I know them and even humble as they are they're good people...

Fast towards then and I "help" pay for a private school for her 2 sisters plus some medical treatment her mother has going through I must say the rest of their brothers try to pinch some money but mostly have day to day jobs and you know how the economy is a hellhole down here so it never bother me helping them since I could...

Now comes the famous D day we got invited to a birthday of one of her nephew and told her she should go first then after I'm out I'll go then I arrive 2 hours later then I ask one of her nephews where is she then he points me at the restroom place the park has so I walk there and I turn the corner to see my fiance hugging and kissing one of her family friend she sees me we both lock eyes of course she panic tell me this is not what it looks like right and I bolt towards my car funny scene that me running out of the situation make the other kids follow me thinking I'm playing a game but her family pick up fast something was happening as she start banging on my glass windows and screaming as I turn the car on and then drive off I have no idea what happen after that just know I felt like shit and went to my parents place and hide on one of their empty rooms...

After a week I had to face her of course and return home to see a whole congregation basically all her family was there imagine 2 parents 8 fucking siblings with kids included and her all came together to try to see if I could forgive if I could see past her betrayal we kinda fight a little but of course I was overwhelmed then I ask the question if the cheating was going for long she didn't answer so I just walk away to a bunch of people screaming at me to come back don't be a coward try to see beyond this you get the idea then 3 days later I ask her to talk alone told a couple of mutual friends to help us and we set a meeting then as I areive first explain to them then told then who he was and all to wich I learn from one of them that the guy she was with was a "ex" from what period I really don't know and I don't wish to know so you get the idea that the moment I learn about that information i drop the meeting send her a message saying is canceled and that I would go pack my stuff and so I did 2 weeks later after the whole fight I was moving out the place back to my parents we fought a lot and had to face each and single one of them trying to convince me to forgive their sister mistake but I end up blocking them and putting my foot down telling them is not their business then her friends pile up even some of my friends too saying is just a mistake and bla bla then what hurt the most was both my parents saying that seeing me like that wasn't right and perhaps I should forgive and fix "our" relationship and yup in this whole parade of people nobody give a damn how I was doing only our relationship to wich I end up cutting ties with most of them besides some of my best friends and my parents on a low contact deal as I move to a 1 by 1 shitty block apartment I could rent fast

Now 2 months after the whole ordeal I paid the last month then cut ties with all payments the house I was renting gone the private school gone her mother medical treatment and pills gone also and I must say try to hold that much while being 2 teenagers 2 retire folk and a house wife who barely finished nurse school you get the idea when the bill came to her she lost it all and came running to my parents to wich she didn't found me so she went to my work and came to talk when I went out she grovel and cry that she didn't want this of us and to give her another chance if it's not for her for her mother I said that I had no attachment more to her or her family and drive off...

Now she has talk with most of the people on my circle again and of course they say I shouldn't be this cruel that i have the money to spare even again my parents why let them suffer after all this time that I should have a little more compassion for them to wich I think who has compassion for me so reddit a I'm the asshole here for cutting the payments and possibly killing grandma because I stop paying or care that they go back to their shithole house because they can't pay the other one...

Tldr: fiance cheated so I cut the payments of her family problems and studies making them go into debt and back to poverty.

Edit: First of all, I want to apologize to all of you for reading such a mess of a text. I wrote it on my phone, but that's no excuse. I should have put it on word first or something. Second, I wanna thank you all for the comments. I was really overwhelmed here around me, and I really needed someone else who could understand my point of view. Besides a couple of best friends, the majority was to forgive and move back, but now I think I get the message I'll try to move on and block for my parents I'll stay low contact since I do understand why they kinda side with her but I don't wanna hear what they have to say and for my fiance I'll try to stay away as much I know it would be hard being in this small town and all but right now I feel like shit and I don't wanna know the whole story of why and when perhaps one day when I get the courage I'll humiliate myself and ask her I thank you all very much for the comments again and I hope you all can have a nice day.