So she pretty much went crazy at the end

She actually became less crazy in the end. She stopped focusing on toxic relationships and found something she wanted to do consistently, not just abandon when she got bored like the pretzel shop or being a lawyer. She actually put work into songwriting and took piano lessons and didn't just half ass it. It showed how much she improved as a person. The songs she had in her head were good enough to be in a TV show for several seasons lol. When she showed a second person the costumes in her head, they liked it. She just had to take all her passion and put it into something useful instead of using it to stalk Josh.

Yes, the show creator confirmed that the song she wrote sucked but they didn't want to show that because it would not have been a good final moment.