I don't know what to say other than it's very sad. This friendship must serve you in some way or you wouldn't hold on to it. Perhaps, you think it will revert back to what it once was. At this point, though, it's dissolved into something quite ugly, unhealthy, and destructive. It's time to look inward and ask: “Why am I still here? What does it say about me to continue in this relationship?”
I'm so sorry about the death of your husband. You may be unwilling to end this friendship because you're not yet ready to face another big loss in your life. That's very understandable. But, if this friend was of no comfort and support after your spouse died, that is further evidence that it's time to move onward and build new, healthier connections.
Change is difficult for all of us, and you're confronted with a lot right now. Yet, you also have infinite possibilities to create something beautiful without the negativity this friend brings into your life. Toxic relationships like this zap us of our energy and bring us down. You're at a crossroads where you can now decide to surround yourself with only positive folks. This will improve your mental, emotional, and physical well-being in so many exciting ways.