Sami came into Jennifer's home and was about to physically attack her daughter. Affair or not, guilt or no guilt, Jen had every right to defend Abby.
I see your point, but keep in mind, it's also Abby's home. I'm also not so sure Sami was going to physically attack her, as we've gotten a good look at what that looks like recently with Nicole. Abby's an adult, well past legal age, and should reasonably be living on her own. It's a strange and awkward thing for me to think about having to reconcile confronting a woman who slept with your husband while trying to see if you have their parent's permission to speak to them about it.
Abby participated in a very adult situation, and she shouldn't be protected from it because she hasn't matured enough to become more independent. Really, where else should Sami confront her? In public? Then she'd be publicly humiliating her. At work? The same, potentially even putting her job at risk. It's not as if Abby has her own space to deal with private matters. If she were involved in a legal situation the police would come to Jennifer's house.
At some point we have to recognize that Abby is dealing with her own choices and actions coming around to bite her, and Jennifer continuing to shelter her from consequences is keeping her from growing and maturing.
To me it's an interesting example of the vast differences between Abby and EJ, and that they are in very different places in their lives. Abby is the one that brought the situation into her mother's home by putting herself into the middle of it while living in the Horton house, and I see no reason why Sami has to be polite given the emotional nature of this story.
I am looking forward to the day that Abby is treated like an actual grown-up on Days. Her peers are getting married, having kids, and starting careers, and she is stagnating. At this point Abby needs a lot more than a lecture from Jen that she doesn't approve of her daughter's behavior. She simply doesn't deserve a soft place to land right now, especially after the Austin situation. Tough love isn't a bad thing, necessarily.
EJ has shown he doesn't care about the company or the assets because he gave it all up last year to free Sami. He has said time and time again he'd walk away from it all for Sami so why should I think that Sami taking the company is going to hurt anything other than his ego.
This, to me, isn't an example of EJ not caring about the company. It's more a matter of priorities. If need be, he'd give up the company and his assets to help and keep Sami, but I highly doubt he'd be content with getting neither. He's not so good at getting nothing, but he's very good at grandiose speeches.