I asked about how long you were separated just to gauge at what age your DD became exposed to parentification.
I am accepting of my experience now, how it dragged me down, how it impacted my own parenting, how I became aware of the issues and still continue to work through them for the benefit of my DCs and to break the inter generational pattern in our families. My marriage did flounder and fail for a few years but we have worked through stuff and are on the same page re the DCs.
It wasn’t too much time and effort with my DD - just a change of mindset really from blaming her for being a nightmare child to being compassionate and appreciating that she was v miserable, sad and self loathing when she was acting out rather than her being malicious and vindictive. That wasn’t initially easy with my previously volatile emotions.
So the approach is to intervene early, de-escalate, calm, soothe, comfort, reflect and try to teach her to do this for herself - rather than add fuel to the fire, escalate, humiliate and punish.
It just meant checking in either end of her day. Having simple predictable routines and catch ups. Being emotionally present and available to her, not busy and preoccupied with my own shit and focused on her needs. It doesn’t take up much time in the day.
I am under no illusion that my DD is out of the woods. I expect her to be vulnerable and she hasn’t done any of the big emotional resilient tests yet - moved out, relationships (eg swerving shit ones, or having her heart broken) - but I know that we have a connection where we treat each other with kindness and respect and she now knows I am there for her unconditionally.
I totally respect your prioritisation of supporting your DCs over a partner. I chose this route at one time. We all only have a finite emotional capacity and all mine was going to my DCs - a partner had to enhance me that not take me away from them.
I hope that the therapy will help your DD and you feel comfortable that all will be well in time. I am quite envious of your DD to be fixing stuff at 23 ... think my own life would have less carnage and would have been more peaceful if I had had that opportunity.
Also I don’t blame my parent for what happened to me (they had suffered a catastrophe) and I don’t blame myself for getting ill with PND and chronic depression thereafter which has hurt my DD - but I do take 100% responsibility for doing what I can to fix myself so that I can re-parent her and make up for those dark days.