Dani downer

Like Debbie downer, only much more drastic; the act of over exaggeration due to something that goes wrong that you think the world is going to end, so one takes everything negatively.

Girl 1: "OMG my ex bf broke up with me like a year ago, I want go go crawl in a cave and live alone."
Girl 2: You're being a Dani downer, there's plenty of fish in the sea.