"Mirroring the lack of seriousness with which we regard it, the term heartbreak has itself become diluted." It's hard to paraphrase this sentence because it's poorly constructed logic and not very well written. I would rewrite it like this..."the term 'heartbreak' is not treated seriously and has become diluted." "When we discover the heroine in our favorite novel fails to choose the supernatural teen suitor we hoped she would." A heroine is a female hero. Hermione Granger is a heroine in Harry Potter. Princess Leia is a heroine in Star Wars. A "supernatural teen" is a teenager with magical powers. Supernatural means something ABOVE nature. God and Angels and Magic are all supernatural ideas. A suitor is a man who pursues a relationship with a particular woman. He wants to marry her! So to paraphrase your sentence I could say..."a male teenager with magical powers is pursuing the female hero in our favorite novel, and we hope that she chooses to be with him, but she fails to do so."

One way to paraphrase the first sentence is: Similar to the lighthearted way it is regarded with, the word heartbreak itself has become unclear. Here are several ways to paraphrase the second one: When we discover our favorite novel's heroine didn't choose the supernatural teen suitor we hoped she would When we learn that the heroine in our favorite novel didn't choose the supernatural teen suitor we were rooting for