The 'Wannabe' hitmaker - who is married to Stephen Belafonte and has two daughters, Phoenix, 11, and Angel, three, from previous relationships - has always been closer to her former bandmates Geri Halliwell, Victoria Beckham, Emma Bunton and Mel C than anyone else, even when they have clashed.
She said: "I've had affairs with all the Spice Girls as far as I'm concerned - they're the loves of my life.
"We are always in touch with each other. We're supportive of each other because we've known each other a long time. When we were younger, it was five girls who had our periods together, so we screamed at each other, but we all made up afterwards."
And Mel - known as 'Scary Spice' during her time in the girl group - will never rule out another Spice Girls reunion after having so much fun with the group during their original formation between 1995 and 2000 and again at their 2007 concerts.
The 35-year-old star said: "The first time we did it, it was sex, drugs and rock 'n' roll and the last time it was all nappies and dummies.
"But I got to travel the world with my four best friends. What could be any better than that?"
The quintet's music is set to be the focus of a new musical 'Viva Forever', and Mel would love to see a film spin-off.
Speaking about the musical, the singer - who starred in 1997 movie 'Spiceworld' with her bandmates - added: "I don't know yet if it's going to be based on our real stories or a fabricated story. We've talked about 20,000 different storylines, but it's down to five and we'll all have to agree. There are no plans for a movie yet, but that would be great."