Melissa Joan Hart still remembers partying with Britney Spears — but says she regrets it “to this day.”

The former Nickelodeon actor met Spears when she was a burgeoning pop star, and revealed Thursday that she still feels guilty for taking Spears to her first nightclub at 17, as substance misuse issues would eventually befall the singer.

“She was underage and young and — but I [was] just like, ‘Let’s go out. We’re just gonna go out and have some fun,’” Hart recalled in an interview with “Entertainment Tonight.” “And I feel really guilty about that still to this day, because I should have known better, being a big sister.” Spears turned 17 in December 1998.

The singer had yet to release her debut album “…Baby One More Time” when she met Hart, who told “ET” they “got to do a lot of press together” at the time. Spears would later endure a difficult breakup with Justin Timberlake and exhibit public signs of distress from what she’d ultimately describe as a feeling of not being in control of her own life.

“I saw that she was just surrounded by people, never able to break free,” Hart, 48, told “ET” on Thursday. “And I was like, ‘Hey, want to come?’ I would go to a club every night — I love dancing and I loved going out, but I also knew to be responsible and, like, when to stop.”

Spears, now 42, wrote in her 2023 memoir “The Woman in Me” that she and her mother Lynne “would drink daiquiris” when she was a child, and that it made them both feel “happier, more alive and adventurous.”

Spears burst onto the scene in 1999 as a Disney alum who’d found stardom beyond the Mickey Mouse Club. Hart, a former child actor best known from “Clarissa Explains It All” and “Sabrina the Teenage Witch,” starred in the music video for “You Drive Me (Crazy)” alongside actor Adrian Grenier. The song appeared on Spears’ debut album and on the soundtrack for Hart’s film “Drive Me Crazy.”

The singer was placed in an infamous conservatorship by her father Jamie in 2008, but successfully fought to dissolve the legal agreement after 13 years, amid a viral #FreeBritney movement calling for her physical and financial autonomy to be restored.

Hart told “ET” that she saw Spears “when she was doing her Vegas residency a few years back.” The actor added that the reunion was swift, and only consisted of “a quick hello and that was it.”

Need help with substance use disorder or mental health issues? In the U.S., call 800-662-HELP (4357) for the SAMHSA National Helpline.