I'm super late on this as I have just discovered this podcast, but I just had to join the forums and say something. This woman needs a friggin hobby. By her own admission her life is so perfect she clearly needs something to be mad about, and this is it. Now I totally understand feeling betrayed. That's valid. But it sounds to me as if she's not even trying to empathize with her so called sister, whom she supposedly loved. All she's focused on is dick.
She starts off this call by saying how her brother is the type of person who's so fragile he probably wouldn't be able to handle the loss of his marriage. (Which clearly she was wrong about.) Ok. If you felt that way...don't you think his wife felt that way too? Have you considered that (no matter how wrong it may be) she didn't want to hurt her allegedly super fragle husband of 20+ years by asking for a divorce, so she made the wrong decision to simply try and find happiness somewhere else while remaining with her husband? It wouldn't be the first time something like that happened. And if the husband actually suffered from something like clinical depression that would make it even harder to just leave him.
The fact that the brother seems to be getting along just fine, even having to tell her to cool it, tells me he has probably come to terms with his role in the demise of the marriage and and while he's probably still hurt is in a place of understanding. Or at least is trying to be mature about the situation, a trait the caller does not possess. You may know your brother very well, you may love your brother as much as a sister could love a brother and y'all might be tighter than bark on a tree. But at the end of the day: YOU AIN'T THE ONE FUCKIN HIM. You ain't the one washing his drawers, you ain't the one puttin the milk back in the fridge for the umpteenth time and you ain't the one dealing with his shit on a daily basis. Maybe he was tired of dealing with her shit and was glad to be rid of her! (Did she really do all those tasks? IDK...these are just examples, folks. Please don't go off on a gender role tangent.) Point is: she doesn't know the ins and outs of their relationship like she thinks she does. She's an outsider lookin in, plain and simple. And it's very easy to judge from the outside. She needs to grow up and as the kids say "Let it go, Elsa".