I think the more you busy yourself with GAL the easier the not caring what they are up to gets easier. I haven't a clue where my wh is, the majority of the time I don't care neither. In his head we are d, and I guess we live completely separate lives. I've had to pull myself away from those thoughts for my own mental wellbeing, as living in the same house- it would drive me insane as he is never home! You've been doing great, you just need another little step back. Nothing we can do or say will stop them, if anything it would push them further to rebel against us. Just focus on you and do what you believe serves your best interests.
With the wayward friends, after the PA and his return, he dropped them- realised they were no good for him. But now he's found some new ones. Eventually they will probably come to a realisation when that person really lets them down and isn't there for them. They're attracted to them now as they make them feel good about them, I don't know if that kind of negativity could last or stand the test. She may well have a realisation moment but how/if/when that would happen, no one could answer.
Just keep focussed on you, she's too toxic to get sucked into right now! There is different schools of thought on the be pleasant/friendly vs full protection no friendliness. And I guess that all comes down to what works for you. I'm pleasant enough to my wh- but if I feel he is taking advantage of cake eating, I pull back. Likewise if I'm feeling a little angry/upset, I just avoid without making it obvious. It all boils down to what works and keeping consistency. Would you want to be with someone being moody, ignoring you, nasty?! I wouldn't, it would justify actions if anything. Just my 2 cents though. I know the tough love thing works for some, and can help the ws come to their senses when they feel the loss of their S. so long as you don't allow her to cake eat, or loose respect, just do what works.
Me 26 H 25 M 4 T 5 Baby born 4/14 BD: 1/15 EA: 2/15 PA: 4/15 reconciling: 4/15 ILYBINILWY- 11/15 ILY-1/16 ILYBNILWY 4/16 ILY 6/16 ILYBINILWY 6/16 Baby due 3/17 BD 8/16