Losing someone you love is so very hard, and I find grief to be one of the heaviest emotions of all. I too lost my Mum, back in 2012 and I still miss her and probably always will. My Mum was my rock, she was always there for me in my darkest times and in times of joy and celebration.
I should mention that I am by no means a professional, so please feel free to disagree, but I don't understand why your psychologist doesn't want you to talk about something that you clearly do seem to want to talk about? That just doesn't make sense to me? But, like I said, I could be wrong.
In the meantime, perhaps if you would like to talk about your Mum and how things are going for you, then you can certainly do that here as much as you want. After all, that's what we are here for.
Take care. I'll be thinking of you. xo