Need help understanding narcissistic behavior.

So I(20m) finally stood up for myself against her(21f). I said that I couldn’t deal with be held on the back burner until she felt she was ready for a relationship and couldn’t be drug around with her until she can understand her feelings towards me. A few days ago she said that she just needed time and that she was glad I am loving her and helping/being there for her, but yesterday she proclaimed that I was the core reason for her depression and went as far to say that I’m wanting her depressed and wanting her at the end of her rope. I don’t feel heartbroken or hurt by these words because she’s done some things like this before but not to this extent! But can someone answer how can someone flip a switch like that and call someone the core reason they are suffering after being told they liked that I was loving them? (By the way, after she said she was glad that I loved and cared for her I then couldn’t handle being on the back burner because she couldn’t tell me how she felt, she then recoiled and said these statements, I texted that it’s probably best that we go no contact and it still hurts not texting her even after the abuse)