Mel B performed energetically at the Spice Girls' 30th anniversary concert in London.
Fans packed the O2 Arena.
Melanie C said the show was heart‑warming.
The night was overshadowed by a reported feud inside the group recently reported.
The dispute centres on management and payments.
The event marks three decades since the group first became a hit.
Later that day Mel B appeared as a stand‑in judge on America’s Got Talent.
A teenage singer took the stage and earned the show's golden buzzer right after the final note amid applause.
The buzzer sent the act directly to the live shows.
Cowell pressed it without hesitation.
Mel B said the singer showed remarkable confidence.