I'll just share my story. You need to do what really works for you and I would certainly at least consider your T's suggestion.
April 2011, Jack broke through my barriers and I confirmed we had DID. Our abuser father had died decades earlier but our abuser mother was still living, fragile and in failing health.
May: I joined this forum and began to talk about all this stuff.
June: We took Jack from our Boston home to eastern Kentucky (Appalachia), where we had never lived, because he was so homesick and in such pain and confusion, we were afraid we would die if we didn't go. We considered then heading northwest to Illinois to confront the mother, who we had just realized from memories had DID just like us. So we could distinguish our mother's good host alter from her two (or more) abusive alters. We asked about what to do in this thread similar to yours. But we made this time for Jack and decided against taking action.
July: we knew we weren't ready but we felt sure time was running out. So I went home and stayed in my mother's house some of the nights. The purpose then wasn't for ourselves but to get the mother to apologize for what she did to our sister, who didn't develop DID and feels in some ways more damaged. But of course, I was confronting her for us too. I told her in graphic detail the incredible cruelty of what she did to us, what I witnessed and remembered her doing to my sister, but I only told so much. She didn't fully deny what I was saying and never said I was wrong but kept asking how could she apologize for something she didn't remember doing. I talked through her host, essentially telling her mean alter Mabel (one who I was sure was able to listen and hear), that if she, Mabel, were able to convince our mother's host that all that I said was true and to send a letter of apology to my sister, I would stop with what I had already said. I was only asking for that one letter. My mother's face was blank a lot as I spoke and I knew Mabel and others were there listening.
** triggers, specific abuse **
I believe Mabel knew that that meant I would leave out the sexual abuse of the father and the threats to remove my genitals that she or someone did through age six.
** end triggers **
Our mother's host was getting off easy, comparatively. I told Mabel I realized that she and the others were only doing what she thought was needed to protect our mother and I actually thanked her for looking after her and protecting her. I believe it's hard for an alter, cruel or not, to dismiss acknowledgement like that.
August: our mother wrote two brief letters, one to my sister and one to me, but sent them both to my sister in confusion so I didn't know it had happened. She left me three phone messages but I didn't return any of them. It felt like I'd said everything there was to say. I left it all in her house over those couple days.
September: the mother died and we attended the funeral. Our sister told me about receiving two letters of apology and gave me mine.
Our mother had DID, with vicious alters and kind parts. We knew from experience, of our own and of her, that she was reachable and it turns out she was. I was a complete mess, from my July visit and for weeks later but for us, it was worth more than I can say. I believed she would never apologize, ever. I didn't believe it was possible but it happened. Even if it hadn't, it was incredibly purifying for me/us. For us, there's no question it was the right thing to do no matter the outcome. In our case, the mother had a condition we understood. In many ways, what had been stuck for us, probably for decades, became unstuck. We aren't perfect or anything but we don't regret any of it.