Rockville Centre singer Ellis Melillo opening for Zac Brown Band at Jones Beach this weekend

Like a musical Zelig, singer-songwriter Ellis Melillo of Rockville Centre often finds herself around famous people. She bartended with future New York Rep. Alexandria Ocasio-Cortez. One of her first professional stage appearances was with the legendary vocal group Jay and the Americans. At South Side High School, she played soccer with future Olympian and Portland Thorns pro Crystal Dunn.

And she met Zac Brown — frontman of the multiplatinum, Grammy Award-winning Zac Brown Band, for which she’s an opening act Saturday and Sunday at the Northwell Health at Jones Beach Theater in Wantagh — through his work on a nonprofit organization with her father.

“I met Zac when I was, like, 15,” says the Mineola-born Melillo, 30, speaking by phone from Nashville, Tennessee, where she has lived for two years. Her dad, chiropractor Robert Melillo, is a neurological researcher and author of books on autism spectrum disorders. His practice's website includes a video by Long Island-native comedy star Kevin James extolling Melillo's work with one of James’ children.

“Zac had a dream of opening a camp for kids that were on the spectrum and not on the spectrum to all be together,” Ellis Melillo says. “That was sort of what drove him to want to be successful, so he could open that camp” — Camp Southern Ground in Fayetteville, Georgia. “He found out about my dad's work and so they got together and my dad helped with the camp. Then both of them got really busy and didn't see each other for a long time.” But in 2019, “Zac invited my dad to a [Jones Beach] concert to come say hi. And my dad asked me if I wanted to go.”

Brown remembered her as a teenager who sang, and asked if she was still doing that. “And I said, yes, I'm writing all my own songs. So he gave me his email and asked me to send him my music. I didn't think he would actually respond, but I spent six months getting all my music together and I emailed it to him, and he responded within an hour.”

The country music star invited her to his home in Atlanta, suggesting they write songs together. Melillo would go there “for a week at a time to write with him.” The result is her five-song, Brown-produced EP, “Cry Wolf,” dropping Friday.

The songs include lyrics of pain and alienation that seem at odds with her outward self. Melillo is a working musician, playing regularly at clubs and festivals. A former sometime-model — mom Carolyn Kerwick was a model whose work included the June 1984 cover of Cosmopolitan Germany — she has a supportive family including two brothers with whom she is close. But, “I am almost 5’10” and I have been this height since I was 13, so it was awkward” in high school. “The height, the braces, the decision to dress like a punk rocker — I was a walking target.” After South Side, she went on to degrees from the University of Delaware and the Manhattan acting school Maggie Flanigan Studio.

And then she worked jobs including one with “Sandy,” as Ocasio-Cortez was known to her co-workers, Melillo says, at the Union Square Mexican restaurant Flats Fix. “She's the one that actually trained me at my job, and then we bartended together for two years. Her work ethic was impressive.” And while Melillo “did have an inkling” that AOC would be successful, “she was just my friend, and at the time I was not paying attention to anything going on, especially politically. … So I would just be talking about boys to her and she'd be, like, ‘Yeah, I'm running for Congress.’ ”