So we've been together for about 4 years both in our early 20s.
Recently in the past 3 months she's become extremely adament that we need to get engaged soon and she doesn't understand what I'm waiting for... This lead to 2 or 3 days of conflict. 

We have spoken about this in length before and came to the agreement that we will wait till we've been living together for a while and then consider engagement as right now I did not feel either of us were ready or financially stable enough. 

Now recently she's brought up the topic again and accused me of not taking initiative and not getting the ball rolling on anything and everything we've discussed went out the window. 
Saying that she fantasized about it happening soon and that everything's there (the dimonds and gold right that I'm supposed to use to make her ring) and why am I not doing anything. 

It's been 3 days of conflict now and she's extremely upset and refuses to speak to anyone about the way she feels. 

Can anyone help me understand why she would be in such a rush as if it was life or death as I can't seem to understand why she feels so strongly about it. 

Tl;Dr Girlfriend want to get married soon and doesn't know why I won't pop the question asap. 
Need help understanding.