Hi,is it ok for me to post?
As I started changing through therapy, my T told me that it might happen like this, that when you become healthier it shifts the balance in some friendships and relationships and that some people will be able to adapt to that and others will not.

It sounds like you have been friends for a long time. I was thinking perhaps there is a middle way? I think it's fine if you don't want to be friends, you don't have to. But if you want to see if the friendship can adapt to the new healthy you, then perhaps don't tell your friend a general statement like they are a narcissist - to them it will probably feel "out of the blue" and like they are being attacked. But the next time they say or do something selfish or hurtful, you could try putting a boundary down or calling them out? Like telling them that you find X thing they have just said/done upsetting or hurtful, could they please not say/do it again.

I've definitely had a similar experience, one example is that I used to never have an opinion on what I would like to do, whereas now I do and I will let other people know what I would like. Most of my friends have adapted to this, and we have stronger friendships now, but one didn't and in the end I have stopped contacting that person.