It took quite a few years before the entire song would see the light of day. The character in the show, Ember McLain, sings about how she was stood up by a boy on several occasions, the final one being when she planned a dinner date (presumably) and later, as she was in a deep sleep due to being so tired from staying up waiting for him, her house mysteriously burnt down. She didn’t wake up, and burned with it, which may give emphasis on why her name is Ember.

In opposition of the idea proposed above, the Wikia page for Danny Phanton states this:

“…One day a boy asked her out to the movies. She waited all night for him to show up, saying, "He’s just running late.” When morning came and he still didn’t show up, Ember gave up on waiting and went home. She was so exhausted that she fell asleep and didn’t wake up when her house mysteriously caught on fire. She died in the flames, which possibly gave her the name “Ember.” Her song “Remember” is based on the above events prior to her death.“

Ember McLain — Danny Phantom Wiki

Ember McLain is a ghost villainess in Danny Phantom. According to one of the directors of the show, before she died, Ember was an unpopular high school girl who strongly dreamed of one day becoming a rock star. One day a boy asked her out to the movies.