Ms. Petras has amassed more than 16 million streams on Spotify, with songs informed by a style and point of view that’s both modern and antique. Much of her frothy approach harks back to the era of “Dynasty” shoulder pads and Cyndi Lauper quirks, bolstered by Ms. Petras’s full-throated vocals and ultrabright melodies.

“There’s a soft spot in my heart for the color and fantasy of the ’80s,” Ms. Petras said while surveying a room anointed with cupcake-shaped banquettes. “My whole theme is fantasizing about the way I want life to be.”

Desperately Seeking Gloss

Ms. Petras has shown uncommon will in making her personal and professional dreams come true. In 2004, as a 12-year-old growing up in Uckerath, a suburb of Cologne, Germany, she joined the first wave of children to receive hormone therapy paid for by German health care. (She had full gender reassignment surgery by 16.)

Crucial to this was the unwavering support from her parents. Both have arts backgrounds: Her mother, Kornelia, is a dancer; her father, Lutz, is an architect. While they are liberal politically, “they’re not activists or anything,” Ms. Petras said.

“I was 5 or 6 when I told them, ‘I’m a girl,’ and they were like, ‘Yeah, we figured.’ My mom had a couple of transgender friends,” Ms. Petras said. “But I was still depressed and wanted to kill myself because I didn’t identify with my body. My mom told me once I’m old enough, I can do something about it.”