How to end a toxic friendship

I really need some help. I need some advice on how to end a toxic friendship.

We have been friends for over 20 years but she has changed alot in the last few years.

Everything is a competition, she likes to brag she is living in the most expensive house out of our friend group and how her son is a genius. The worst thing she did was seem to take pleasure in the fact another friends son was autistic, bragging she knew long before anyone else.

I'm currently off work at the moment due to depression, stress and suicidal thoughts. I am getting better with medical help.

About 3 months ago at my lowest she invited me out for birthday drinks. I explained everything to her and that the antidepressants I was taking were making me tired and dizzy so I declined. She seemed sympathetic at the time but I have not heard from her since. Not even a text to check in.

I feel like now is the time for me to clear all the negativity out of my life but I dont know how to end a friendship.