The outspoken pop star revealed she and Geri had been intimate during an appearance on Piers Morgan's show "Life Stories" and immediately texted her bandmate to let her know what she'd said.
Mel tells the Mail On Sunday's Event magazine Ginger Spice had no problems with her pal's confession, but then things got out of hand.
"Things got really pumped up in the press and on social media, and yes, it was difficult between Geri and myself for a while," she says. "I texted her on the night I did the Piers Morgan show and explained what he'd said and how I'd answered and she was fine with it. The problem was it then got hyped up into a much bigger story, and it didn't help that we were just about to begin rehearsals (for the Spice Girls reunion tour)."
"It was awkward. We hadn't been back in the situation of being together every single day, being on stage, rehearsing, getting ourselves back into Spice Girls mode, and then all the headlines about our relationship were thrown into the mix, which was pretty bad timing."
Mel B also told the publication that her Spice Girls bandmates are different women to the stars they were when the group was topping the charts all over the world: "We have all grown up...," she explains. "We've all changed. Mel C is so much more chilled and sorted and knows exactly what she wants, as is Emma. Geri is different. She's married, she's got kids, she's not the same outrageous Ginger she used to be. That took a bit of getting used to for me."
"I've changed. I've been through 10 years of a deeply abusive marriage. I've lived a lie for a decade and I've come out of it wanting to be so honest and so up front about everything."
Mel B also admits she and Geri have resolved their differences thanks to a heart-to-heart chat following the band's last reunion show in London in June.
"Geri and I are in a good place now," she adds. "On the last night at Wembley, Geri did something which, I think, meant more to me than any of the other girls. She said sorry for leaving the group back in 1998. We had been so close and then she just left and never really said why and never really said sorry until a few weeks ago."
"She gave me a massive hug after she said it and both of us had tears in our eyes because we knew, deep down, it had needed to be said for a long time, something that had rankled between us."
The "Wannabe" singer is now determined to regroup the Spice Girls again for an appearance at the 2020 Glastonbury festival.
"My plan is for all five of us to do Glastonbury next year for the 50th anniversary," she smiles. "I'm in the process of persuading Victoria to do it. And I will make it happen."
Victoria Adams bowed out of the reunion tour this summer.