Feeling stuck in a “cocoon” of terrifying depression and anorexia, Lindsey Stirling wondered if she would ever experience feelings of happiness again.

But after quickstepping around the Dancing With the Stars ballroom in a stunning monarch butterfly-inspired outfit with dance pro Mark Ballas on Monday, the YouTube star opened up to Et about how she was able to emerge from her dark struggles.

“I feel like I had to go through my own cocoon process,” she told Et’s Cameron Mathison, explaining how she related to the transformative theme of her performance, in which she and Ballas started out as caterpillars then emerged from a giant cocoon as butterflies. “I think everybody does, and for me personally, it was that I struggled with anorexia and depression for years and at certain times I thought, ‘It’s too hard to get out of this.’”

“I was stuck in a caterpillar phase, but I had to...