Truth / reality / are necessarily subjective, I think.
This is true. (

). And there are some things that we cannot know the truth of. But there are others where people who ought to be able to see what we can see, for some reason do not, or cannot, or will not. Whatever the reason. And they distort reality. Not just subjectively, but even in an objective sense.
I am very suggestible, and it takes me a long time to fight back from this kind of topsy turvy thinking. And it is exhausting.
October, a more precise question from your T would have been:
Do you really believe that? Is that your truth?
and then
Do you really believe that other people think that too?
If she had asked this, then I would have said, no that is not my reality.
Then I would have said, it is not the reality of everyone, but of most people that I meet, most of the time. So much so, that the voice of reason is drowned out, and I lose touch with what reality is. Or maybe I wouldn't have said that, but I might have eventually worked it out.
But even this t doesn't want the truth, does she? She needs me to protect her from the truth that I cannnot cope for three weeks without support. And I protect her by coping with what cannot be coped with. I become the keystone, when I am actually the weaker of the two.
This is like C at school. I took her out because all the coping was borne by her, when she was already unwell. I transferred the coping to me, the LEA, her tutor, the school; anyone but her, so that she could recover. But this is not anyone's 'truth' but mine, seemingly.

Trying to be stronger. It may be nobody's truth but mine, but my truth is the one that is happening; I am the one that counts. Makes me strong, even though not strong, if that makes any sense. Others can have their opinions, but I am the mother.

Thanks everyone for your help. Much appreciated, as ever. (((Hugs)))