I think it is great to say what is helping you and telling your mom not to diminish what you are finding to be good for you - I don't think telling your mother she is wrong about what she would find useful/ is great.
I really don't think the things that are helping you would help everyone - evidence based or not (and I don't believe in their biased testing to begin with -so there is that). And sometimes it is such that one will try something if presented in a way they can understand it versus how an approach works for someone else.
If I was told to write an empowerment letter I would tell the therapist to F off. I tried it once and it did not help me at all and I found the language/ attitude of the therapist quite patronizing.
That language would not be useful to me. But a similar sort of activity might be useful if presented to me in different language.