Something along these lines
I appreciate all the good memories I made with you when I was small, but knowing now all the terrible things you did and said to my mom
and that you keep doing.
I can't see you the same way anymore. After reading this, you'll probably think she's been pouring poison in my ear but actually I'm just not sheltered from it anymore.
I can't see you anymore. Not because my mom said anything but because I don't want to
There's just so much on my mind I can't even say it all