The "King of Queens" actress was a devout Scientologist for 30 years before she famously quit the church in 2013, and she has since become one of the organisation's most vocal opponents, highlighting the questionable practices of the religion on her TV series "Leah Remini: Scientology and the Aftermath".
She has also spoken about her experiences with other celebrity Scientologists, and last year she claimed Will Smith's wife was a member.
"I know Jada's in. She's been in Scientology a long time," she told The Daily Beast. "I never saw Will (Smith) there, but I saw Jada at the Celebrity Centre..."
Jada subsequently dismissed Leah's claims, explaining she has taken part in many different religious customs, but she is not a Scientologist.
"I have studied Dianetics, and appreciate the merits of Study Tech... but I am not a Scientologist," she wrote on Twitter. "I practice human kindness, and I believe that we each have the right to determine what we are and what we are not. NO ONE ELSE can hold that power."
However, Jada and Leah have since sat down to film an episode of Smith's online show "Red Table Talk", and realised experiences from their pasts led to the feud.
"You have to treat people with kindness because you don't know what they're going through," Jada tells People magazine. "When she told me her story, I had so much more compassion and it reiterated the necessity to just be gentle and kind because we're all f**king devastated."
"It was really beautiful and she reached out to me," she adds. "She was much more bigger than me in that way (sic). It was nice to reconnect and release ourselves from all that nonsense that doesn't matter."