I really relate. That was great advice your therapist offered. When new boundaries are set, others typically don't know what to do. They might pull out all the stops to try to maintain homeostasis. Just continue to hold this boundary so that you may build on it.

I used to get really angry at my parent's manipulation or lack of response, ect....just nothing along the lines of health and healing. I'd get so angry, they'd deflect it, and eventually I'd just take it out on myself. They didn't care that I was angry or hurt - so I found myself suffering while they were "fine". If they wouldn't validate it....there are many layers, but I just struggled with it all. Anyone, especially your parents, that instills the belief that your feelings, experiences, and perceptions are wrong....to me, that is a form of emotional abuse. It's important for you to follow your feelings - if you loathe the idea of having to contact them, playing the role of the parent - then don't. Stay strong, and I'd guess that when they do contact you, there will be some guilt and shame thrown at you. Don't own it. It's not yours.

I try to channel "calm and assertive" when trying to establish my own boundaries. It helps me feel like I am taking back my power. That being said, anger is normal and natural - so express whatever you need to.