You really are between a rock and a hard place. I think you're onto something about countertransference and her daughter. If she has seen you like a daughter in the past, and is having an issue with her daughter about this recent relationship change, it's going to be a sore spot, no matter how correctly you try to frame it. She may just be unable/unwilling to go there with you, and it really isn't about you.

That leaves you in the position of perhaps needing to give her some space and time on this issue, while limiting your work to something rather defined and basic, if possible. I think eventually, you'll need to deal more deeply with all this, but maybe it just can't be done right now.

It's annoying to put it on hold, but if you value the relationship, then maybe it's worth it. Or perhaps a break would help.

Although the circumstances were very different, I experienced a similar feeling disconnect with my T at one point in therapy. He also saw me as a daughter in our relationship. I didn't understand what was happening, but it felt as if he were putting the issues I was bringing up aside. As though he wanted to "settle" my life and prepare me for ending our relationship. There were a couple of difficult months while this was playing out.

In hindsight, we surmounted the disconnect and my frustration when his health issues (of which I had no knowledge) culminated in his needing surgery. Talking it through after, he was dealing with fears of his own mortality, and the countertransference was revealing itself in his need to protect me from what was happening, yet also prepare me for a future without him. It all led to increased closeness between us, and eventually, a good termination when he retired. But in the interim, there was nothing I could do to shift him to addressing the issue. So I do wonder if some aspects of countertransference are at play here, in which case I think it will unfold only on its own timetable.
ETA: OK, just read your up-date. Glad to hear she admitted her RL was interferring. Sounds like you will have a good session next time!