I know this has been said before, but bears repeating-- validating is about FEELINGS, not behavior. And I think it comes across as condescending when the person trying to validate is just saying the words and doesn't actually give a $hit. People can tell. Try to put your own ego aside and be actually curious about what the other person is saying.
Even if what you're getting from your S is "I want a D"-- okay! I know it helped me a lot when I went from hearing my H say he wanted to (maybe) move out and in my head just furiously composing all the reasons why that was a stupid idea for the kids or whatever to setting myself aside and just really listening and realizing-- this is truly how he feels and I needed to actually understand and accept that. It helped me tremendously towards detaching.
I don't think your responses need to be exploring her feelings and asking leading questions to get her to open up more. I think it can simply be I hear you, I'm listening, I see you as a person rather than the enemy who is trying to break up my family and take my kids away. In my sitch when my H would say things like he was thinking about moving out (and I got past the arguing back phase) I would just say, okay. I understand. I'm not stopping you. It takes the wind out of their sails when you don't argue back. Now I wasn't going to do any of the legwork for him, or pat him on the head and say it was a terrific idea-- if he wanted to move out he was welcome to, but I wasn't going to be an accomplice or make it a mutual decision.
All the GAL sounds good.
The observing comment is condescending. But who cares? Of course she says $hit like that. She's a WS. Don't let it bother you for a single second. Getting up in arms about her being condescending is just continuing to be attached.
My recommendation for you is to simply continue to focus on that which you can control-- YOU-- and recognize and let go of that which you cannot (everything else, but particularly your W). It seems to me a bit like you swung from worrying about every single thing you said to her and tiptoeing around to being kind of rude and cold (I could be totally reading that wrong, if so I apologize) but also still hoping that you acting in this way will cause her to do or think X, Y, or Z. It is still trying to control her behavior and having expectations.
One last little piece of advice-- I would recommend beyond your self-help book to read something totally unrelated to your sitch, or watch a movie, or hang out with friends who don't know what is going on and you can just talk about all sorts of other things-- I think when you let your situation seep through every part of your life, it is exhausting. Carve out something that isn't about improving yourself or your M or whatever. Just relax and BE and remember that everything is going to be okay, no matter what happens, as long as you remember what is important (for me it was focusing on the kids and being the best mom I could be).
Me (46) H (42) M:14 T:18, D9 & D11 4/19 - 12/19: series of escalating BDs 9/20 - present: R and piecing