She designed Taylor Swift’s engagement ring. Business is booming.

She was 25 at the time, and metalwork was just a hobby. Still, she recalled telling him, “‘I want to see my name in lights,’ verbatim. And he said to me, ‘You’ll never be the next big jewelry designer.’"

Hearing her tell this story, you wish you could have seen the look on the guy’s face on Aug. 26. When Taylor Swift shared a close-up of her ring in an Instagram post announcing her engagement, it didn’t take long for Swifties to trace the engraved yellow-gold ring to Lubeck. Three years after launching her independent label, Artifex Fine, Lubeck designed the most famous ring of the—year? Decade? Century? And without traditional marketing, ad campaigns or gifts to influencers or celebrities.

“I think there was an element of me that was like, ‘Really? Me?’" Lubeck, now 30, says in an interview at her airy studio in New York’s Long Island City.

In a radio interview, Swift said she’d shown Kelce a video made by Lubeck a year and a half before their engagement. “I just thought her stuff was so cool," she says. “And he was paying attention to everything, it turns out. When I saw the ring, I was like, ‘I know who made that, I know who made that!’"

Lubeck is an expert at social media, walking followers through her creative process in her languid voice. She says she sometimes spends hours listening to Instagram Reels with her eyes closed to pinpoint song clips that will likely make for a viral Reel of her own.

Her first brush with virality came before she launched her own line. Her father, Jay Lubeck, is a goldsmith in Neptune Beach, Fla. She recorded herself engraving a box of his loaner rings, simple bands that are given to customers to wear while their jewelry is being repaired. One of the videos hit 9.9 million views. After that, she started to receive requests from customers to design their engagement rings.

This year, she released a “vault collection" where she took gems she’d been gathering for a year and fashioned them into pieces. When it came out this spring, all of the pieces under $25,000 sold in two days, totaling $65,000. Everything over $30,000 (“my masterpieces," she calls them) sat around—until the Swift news broke. The $100,000 of remaining inventory sold immediately after the announcement.

Ever since, Lubeck, who has elfin features and long, curly hair, has been getting recognized at gem shows, a bake sale and in New York’s Diamond District and Times Square. People ask to take pictures with her. Her social media following more than doubled to almost 400,000. Three of her rings are going up for auction at Sotheby’s. Estimates are $70,000 for a 4.05-carat old mine cut diamond, $80,000 for a 5.48-carat ceylon sapphire and $150,000 for a 8.66 fancy brown diamond, with bidding running from Nov. 10 to 13.

Her rising profile means Lubeck sometimes sees comments about herself like, “Her father is a jewelry tycoon." “I jokingly will call my dad now and be like, ‘How’s the jewelry tycoon?’" she says.

Her business is self-funded, she says; the money that she used to buy materials for her first collection of pendants came from spending all of her savings on three pieces of antique jewelry and then flipping them. She describes her dad’s store as “a small workshop in a tiny little beach town." She started working there a few years after graduating from college. When they had extra free time during the pandemic, Jay asked his daughter if she wanted to learn how to make jewelry.

She took an engraving course. “I was like, Oh, my God, this is it," she says. Tiny swirls, minuscule flowers and delicate lines, all etched by Lubeck’s hand, have become her brand signature. When she travels—to places such as Hong Kong for gem shows and Italy—she finds inspiration in ornate architecture, windowsills and door knockers.

“The handicrafting quiets my brain and it’s Zen and it’s peaceful. You make these tiny little micro-movements with your hands," she says. “Can we make it even smaller? Can we make it even better?" Lubeck launched Artifex Fine, named after the Latin word for craftsman, in 2022. She moved to New York last year to focus on her line.

Lubeck describes the style of her pieces as ornate and antique-inspired. “You don’t see that engraving in modern jewelry," she says. She loves colorful and older stones, like the old-mine cushion cut diamond in Swift’s ring. “Modern cuts sparkle like a disco ball," she explains. “They’re cut to be as sparkly as possible. The mine cuts are a lot softer." They also have larger facets and are asymmetrical, she says.

Lubeck declined to discuss further details about working with Kelce, or whether she’d be designing Swift’s wedding band. But the engagement ring is so distinctive that it’s hard to imagine another designer’s handiwork pairing with it.

“When you look at the ring, you just see Taylor," says Sarah Chapelle, who runs a comprehensive archive of Swift’s outfits on her blog, Taylor Swift Style, and wrote a book by the same name.

“It just feels so romantic and storied," Chapelle says. She says she spotted a tiny “T" engraved on one side of the ring and thinks it’s likely another is on its other side, referencing the couple’s “TnT" nickname. Lubeck declined to confirm whether this is accurate.

Lubeck’s goal, she says, is for her jewelry to make people feel awestruck. She says it might take her a while to release a new collection, but “I want your jaw to drop," she says. “That’s the only criteria."

Write to Lane Florsheim at lane.florsheim@wsj.com