None of Don’s “mistresses” have so far bothered me as much as Sally’s teacher does. Almost everyone is cheating in this show, and yes, that’s awful and amoral no matter who is doing (with the exception of Betty tbh). But none of Don’s side pieces have ever had an established personal contact with his family, especially his daughter. They were just random women, horrible as he was, who did it possibly because presumed ignorance is also bliss, and who knows, maybe at least one of them would have turned him down, if they knew his family personally. Sally’s teacher is different. After relating to Sally’s process of grieving so personally and overall giving the airs of self righteousness, she’s actually the first one to start acting all messy and pretty much does everything short of making a direct move on Don to let him know she’s ‘available’. Fully being aware of just how destructive to the family, and especially his kids, this shit would be. Don’s an established piece of shit, ofc, but there’s something extremely conniving and toxic about her behavior, too.