Beckham, 38, will meet her ex-bandmates Melanie Brown, Emma Bunton, Melanie Chisholm and Geri Halliwell here in West End on June 26, reported Sun online.
It will be the first time they would be seen together in public since their 2008 reunion tour.
"There's been rumours knocking about that Victoria wasn't going to show - but she always made it a priority. She was never going to miss the launch and is looking forward to seeing the rest of the girls. The musical is a proud moment for them all. It will be emotional," a source said.
'Viva Forever', named after the band's song, is written by Jennifer Saunders and celebrates the girl band's music.