The model and KORA Organics founder added that she family share "all the important milestones together" and that she's found a real friendship with Katy.
"I love her. I mean, it'd be safe to say that I love her more than Flynn's dad," she joked.
Miranda added that she and the Firework hitmaker hit it off from the moment they met at Orlando's Malibu home.
"When Orlando started dating Katy, I remember he invited me over one time and she was there, and we just immediately got along," the mum-of-three recalled. "I saw how she was with Flynn. She was very playful with Flynn. She was not trying to be his mum. She was just being friendly and fun, and that's all you can ask for."
"We hung out by the pool at his house in Malibu and then there was like a little party up the road, and we all went to it together and it was like, 'Oh, this is great!'"
Miranda has spoken on numerous occasions about their happy blended family dynamic.
"When it comes to special occasions, when we have to be together, we work it out so we have compromises [about] what is the best for our whole family," she told Drew Barrymore on her chat show in November 2020.
"We really do always think of what is the best thing for Flynn, and I just think that's the most important thing."
WATCH BELOW: Miranda Kerr bonds with Katy Perry over their similarly scheduled pregnancy. Post continues after video...
Whilst Orlando has found love with Katy with whom he shares daughter Daisy Dove, Miranda has been married to Snapchat creator Evan Spiegel since May 2017.
The couple share two sons - Hart born in 2018 and Myles born in 2019.
"Sometimes I have to just stop and pinch myself because we have three healthy children, we're both doing what we love," Miranda told E! News in February 2021.