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