My T responded in a similar way to something where I was feeling anger, but it didn't seem like he wasn't validating my feelings. And I know for sure that he's all about getting me to express my emotions. IDK - maybe it's some kind of balancing thing that they teach in T school

But I WAS mad at my parent and at that point I really didn't care if they had reasons for doing what they did, and I was in no mood for any kind of forgiveness. I realize that that's what we need to do ultimately - make peace with what happened so we can live with it, and move on. But I think we need to fully acknowledge and express our anger FIRST, especially if we've been holding it back for a long time.
Is it possible your T validated your anger at first, but then when she moved toward talking about your Mom's POV it really set you off? I've found that when I'm really showing anger in the therapy room, I just can't help dump some of it on T.

After all, he's right there in front of me and whoever I'm angry at it isn't. Or maybe I'm just angry at the whole world, and he's an easy target. IDK.
But I think you're doing great! I hope you have a good discussion with
T over this, and feel more validated afterward. Good luck!