NTA I understand where your son is coming from, I went through a similar thing with my mom where I was never comfortable around her and she tried to force me to trust her and open up to her which strained our relationship even further. it’s not a personal attack on her character that your son can’t trust her, that’s something that may come with time and it may not, either way, how someone deals with trauma is unique to them and her judging the way he handles his trauma is quite frankly cruel, he should be in control of when he feels comfortable to open up to her, he is not obligated to open up to her or like her just because she’s a part of his life. I think it’s awesome that you’re sticking up for him :)