H.W.
Here's my advice and you can take it or leave it:
Your relationship with your daughter is extremely dysfunctional. You cite all that you have given up for her without acknowledging how much she obviously has tried to give back.
I was once at the crossroads of a similar situation. My own mother, who I was never, ever 'good enough' for, escalated the demands and insults to the point that I told her we either went to counseling or I was done. Done was not not walking away out of anger; "done" was my only option for self-preservation. Having a parent telling you constantly how you aren't doing enough, being enough-- it does effect nearly every other relationship in ones life. It is draining and destroying. She has grown. You haven't.
It's been 15 lovely (yes, lovely) years now that I have not had her in my life. She made the choice to stay 'the victim', she refused to see her role in our relationship and how she was damaging me. She has never met her grandson or my husband. I am a better parent for the hard (and often painful) work and growth I invested in myself. I'm a better friend and wife. My life improved so much...
I have not one--one-- shred of regret.
Life is about choices. You are choosing to tell your daughter that she is responsible for your happiness. She isn't. YOU are. (Frankly, if I'd received a letter like this from anyone like the one you wrote her, they would be dead to me. It is so incredibly toxic.) The fact that she wrote back speaks *volumes* about her kindness and integrity -- the qualities you so question in her. She offers to go to counseling, not to change who you are, but to change the dynamic so that you aren't hurting each other. The inner changes come through our own revelations about our own thoughts and beliefs, where they come from, and how they effect our behavior. They come from finding empathy for the person we feel conflict with, something I think you would benefit deeply from. Most healthy parents would be delighted that their adult children are making the life they want for themselves and experiencing the sweetness and love that comes with being a healthy parent. You sit in your bitterness and just feel 'she owes me'.
I tell you all these things as a cautionary tale of what can come if you choose not to respond to her gracious offer. I grieved the loss of my mother -- and her inability to want to get better and change-- and then, eventually, I moved past that and into a newer, freer world I will never, ever give up for her again.
Don't miss out on this. You have a path offered before you. Consider it a gift, get over your pride and anger, and take that step out in faith that this might make life better for both of you.