Between being a judge on America's Got Talent and preparing for a Spice Girls mini reunion, Mel B is entering one of the busiest times of her life -- and she dished about it all to ET!

Mel B, Geri Horner (formerly Halliwell) and Emma Bunton have a mini Spice Girls reunion in the works, with the trio reportedly planning a one-off concert in London next year. But, of course, they will be two Spice Girls short as Melanie C and Victoria Beckham will be absent for the affair.

WATCH: Spice Girls Serenade ET in 1997 After Releasing Their Debut Album

"They're there in spirit," Mel B tells ET. "But we have a few little surprises that hopefully everyone will be excited about."

The three ladies will be performing under the name Spice Girls - GEM, which is an acronym using the first initials of each of their first names.

But if Mel B's America's Got Talent cohort, Heidi Klum, has her way, they might have to add an "H" to the group name. She sent a message via our ET cameras.

"Mel, I love you and you know if one of the girls is not coming, I'm going to be that missing Spice Girl," she said with a wink. "I'm going to be Sweetie Spice."

WATCH: Spice Girls Tease Fan Party on 20th Anniversary of 'Wannabe'

"I love you to bits, Heidi, but maybe next time," Mel B responded with a laugh.

Even with so much on her plate, Mel B has still found time for fitness. The 41-year-old singer revealed on Instagram that she's dropped 30 pounds in the past few months, and shared some bikini pics to prove it.

She filled us in on her three tips for losing weight.

PHOTOS: Hollywood's Best Bikini Bods Over 40

"Sex, sex and more sex," she joked.

Watch the video for more.