Narcissists have fragile relationships with others, as their overblown ego means they often take offense at the smallest imagined slight & will suddenly cut people out of their lives or punish them in some way for 'insulting' them.
She became silent. There were no longer any words to describe the absence of emotion within her heart. She went from arguing to being upset, now feeling nothing at all. She became silent because you were no longer worth fighting for.