What's the best course of action?

I've been in a relationship for for years now and have been hitting communication problems. Arguments start before anything even happens, things that are small become drastic, things that are big undermined. When she gets mad whether she's right or wrong she breaks down, won't talk, listen and the whole day is ruined. How do I end her stupid way to control arguments? How do I get her to talk first? At the slightest problem or confrontation things get escalated fast. From insults to stone walling i'm tried of her attitude.