My DH uses the silent regularly. It's considered one of the cruelest forms of emotional abuse. It hurts.

I've dealt with it by detaching to the point of not taking it personally and accepting the silence. Going off and do my own thing.

If it's a relationship, it's really more like a parent-child, not two adults. It hurts, it's not the relationship it should be. If you stay or are stuck, realize that it's her dysfunction, a symptom of not knowing how to get her needs met in a healthy way, and try not to engage in it. Easier said than done, I know.