Why are you getting involved in and getting yourself worked up over her medication? You created friction, let it become and argument, and fed her justification for wanting out. Sorry, but if she's an adult and has a doctor prescribing for her, the extent of your involvement in that should probably just be feeling good that she's making an effort to manage her healthcare.
Again, why have an opinion of her anxiety issues flaring before a therapy appointment? You sound very involved in her head. If analyzing her behavior is helping you to understand her and where she's coming from, such as if that understanding makes you more patient with potential outbursts the day before therapy, that's probably helpful. The way it was written sounded a little more condescending than compassionate - maybe I read too much into your words?
IMHO it sounds like you need to focus on the DB solution-oriented system. Try something for a while - a couple of weeks, not just one incident, and take note of whether it draws her closer or pushes her away. Sounds like your we-love-you in the moment that she was having difficulty was sweet, unrehearsed - did you find any backlash or negative effect from it? Sounds like your inquiries into her mental state or challenges of her medical decisions would have a negative effect. Watch how she responds to your 180s and if going darker doesn't sound like the right thing, try what you think is right. See if it works and if so keep doing it.
If your assignment sounds pushy why not ask W if it sounds like something she would like to try or if she thinks it sounds too pushy.
Hang in there!
Adinva 51, S20, S18 M24 total 6/15/11-12/1/12 From IDLY to H moving out 9/15/15-3/7/17 From negotiating SA to final D at age 50 5/8/17-now: New relationship with an old friend __ Happiness is a warm puppy.