There are times when a line like this, leaden with its density of language, is the zinc-plated fodder of college writing workshops. It's at this point, however, I'd like to make a plug for sincerity, and sincerity as a value that thrives on context.
In the context of a bad short story, a short story supersaturated with the hypersincerity that only a 19 year old can muster, the line "The sun was caught playing unashamedly in her auburn hair, setting our world on fire with giddiness" is the pair of concrete shoes carrying the victim to the bosom of the briny deep. But in the context of the piece, with its risky and real sincerity, the line gets a pass. The line is somehow ok as the gilt filigree hammered around the periphery of the write-up. It's ok because it is sincere, and under the correct circumstances, I admire anyone with the courage to be sincere. When you are sincere, you are as exposed as the first time you ask someone to the prom. You have made your intentions known, shown your hand, they have your number. People can now tease you mercilessly, manipulate you, or just think you're stupid. When you are sincere, you have to somehow trust that the legitimacy of your thinking and emotion will connect with the person you're speaking to. When it does happen, and the gamble pays off, it can inspire giddiness.