It's a tough call there QS... Hopefully she will write down something in text that you trap that offends THEM and you can share that with them...
They just don't sound particularly educated which is common... Most people do not understand infidelity as an addiction... They have seen too many movies... And they don't understand wayward spouse problems either... they just think the person is doing what's best for them and their jugement is stable....
I think you know better, but the more people that know better the easier its going to be...
She's going to resist your efforts to improve the home, but you do have to accept that they make a difference to her, even if she is too stubborn to admit it to your face.
The chats she has with her friends are there to help her reinforce herself, she likley has a lot of suppressed doubts about leaving and needs a cheerleading squad to support that.
People who are committed to leaving don't need to make a huge production out of it... I suspect she's making such a dramatic event out of it because she's frightened...