The pair reunited with the rest of the group in London earlier this week for the launch of their new musical Viva Forever.
Beckham came under fire from critics after failing to smile during a photo call at the launch.
The Mirror reports that Chisholm has now come out to defend the fashion designer, arguing that she was exhausted from travelling.
"It's annoying when people say Victoria wasn't smiling or didn't want to be there. She really did. It was a flying visit and both her and Melanie [Brown] were exhausted as they'd flown in from Los Angeles," Mel C explained.
"She was so tired but, among us, she was on great form. It's great that she decided to make the trip at all. She's a very busy lady and in the middle of designing a new [fashion] range. It's certainly not easy for her."
Beckham has admitted in the past that she looks moody in photos, but insisted that she isn't in real life.