Is AUTHOR wrong in the post ? POST : I doubt the responses to this are going to completely change my mind on what I've decided to do, but I'm looking for someone to "check my work," if you will. It's a rather... complicated situation.

About two years ago, I started dating my wonderful girlfriend (we'll call her B in this situation). Not terribly long before her and I started dating, my girlfriend's mom stopped dating her boyfriend of ten years (we'll call him A). "A," as I found out later, was someone who lived in the house but didn't contribute much financially, emotionally, or physically. B never had a good relationship with A, until things marginally better after B's mom stopped dating A. This is all important because:
A little less than one year later, A buys a local business and hires "B" to work there. As a manager,"A" brings on the woman who was working there for around four years and is practically the face of the business -- we'll call her S. S is extremely charismatic, one of the most interesting, devoted, and (unfortunately) boundary-less people I've ever met in my life. A few weeks after the whole transaction happened, I went to go see where my girlfriend worked, started helping take out trash and other misc. things, and was eventually hired after she had really no reason to -- I am very grateful for the opportunity I was afforded.

"S," during all the time I've known her, successfully completes the divorce process with her ex-husband, a relationship she never wanted in the first place. Because "S" has a boundary problem, she became the manager and quickly took on more than she could handle. "A" turned into an absentee owner who knew nothing to begin with, and he quickly tasked "S" to deal with all the stuff he didn't know how to do -- day to day operations of the business, hiring and firing employees, etc. -- on top of other stuff like depositing his personal checks, coming into the store whenever he felt like it and demanding a meeting with her (there were three people there including me and she couldn't really get free), and generally has to handle all the high level administrivia and most of the low level daily work because he couldn't hire another person. She was expected to do everything without much access to anything (including bank statements to reconcile against), and eventually got burnt out. Oh, and "S" got really sick. She doesn't know exactly what she has, but likely something autoimmune. She was very much pushed to her breaking point throughout the year. There was tons of miscommunication, no communication at all, etc.

TL;DR of above information: "S" is manager for "A's" business, and "S' is pushed to breaking point for many reasons. Miscommunication was rampant, and made things terrible.
"B" and I became really discouraged throughout the year as we watched her lose a ton of weight, struggle with the day-to-day of the business given the seagull owner, and raise two single boys. Eventually (recently), "S" rightfully decided to leave the business. "B" commits to leave too, very loyal to "S," and I had decided before I even joined the company that -- given what I had known about the personal and business practices of the owner -- to leave if "S" left.
"S" put her two weeks in. "A" comes to the business, never talking to "S" while "S" wasn't there. "A" says that "S" has 'brainwashed' "B" and starts proclaiming "S" as a bad manager. There was allegedly some yelling, lots of tears, etc. Because "B" &amp; "A" have a personal relationship, and because "B" feels really strongly about how "A" only ever shows the 'business' side with no empathy, "B" says she doesn't want a relationship anymore with "A" because of how he has treated "S." "B" puts in two week notice.

It's now Thursday morning, I'm opening the store, and "A" is going to talk to me as the only one at my location (there's two) that knows about the day-to-day operations of the business. Mentally, I had made a list of things that I didn't like about how he is and what I would need to stay for a while:

* I had no patience for hearing anything even close to "S" was a 'bad manager' after what I saw her do for him, how hard she tried, etc. If she was suddenly useless to him, I don't want to work for a person who treats employees that way

* I wanted "A" to commit to working in the store a little more rather than just leave, by his own free will, without me asking him to

* I didn't want to hear anything about "B."

What actually happened was:

* He said that "S" was a bad manager, and that if she didn't train any new employees, she was useless and should just go immediately

* He bashed "B," saying that "she didn't have a right to her feelings"

And that was enough for me. I told him I was actively looking for another job, and I would try to give my two weeks. I eventually do get another job through a connection I have with my (now old) job, contingent on starting immediately. I submit my resignation.
Fast forward a few days, "S" is showing a person from the other store how to do things. The other lady from the other store is becoming overwhelmed and goes to the back to talk to "A." While "S" is talking to a customer, "A" calls "S" a b****. "S" walks out, given that "A" needs "S" more than "S" needs "A." 

Everyone's now gone.

Before I even left, I had a feeling I'd be the only one in the position to want to help the business. I was strongly discouraged from staying. "S" was on the phone with me one night last week (when this all went down) threatening to fire me if I attempted to stay and help. That got "S" off my perfectly good side and on to my more skeptical side. On top of that, I've now got "B" mad at "A," and given "B" is my girlfriend, she's already stated that if I help "A" in any way, she would be (probably rightfully) pissed at me. I still want to help, and I don't want to live in a world where people don't help others -- even if they don't deserve it. 

On Tuesday, I plan on going in for a few hours and helping whatever way I can, in spite of "S" and "B"s wishes. AITA for going to help them, even though my old manager and girlfriend don't want to?