Diversity took to the stage earlier this month with a dance routine inspired by the Black Lives Matter movement.
While there have been over 24,000 complaints about the performance, Alesha praised the former BGT winners for their work.
She told the Daily Mirror newspaper: "On the day of the performance, the camera didn’t actually pan to the judges and I was sitting there in floods of tears.
“I had this overwhelming feeling of ‘Wow I can’t believe I am watching this on BGT’. It felt really important.”
Earlier this week saw Alesha's fellow judge Amanda Holden show her support for Diversity and Ashley Banjo as complaints poured in.
Appearing on ITV's Good Morning Britain, Amanda backed the routine and said the response proved it was necessary.
"It is extraordinary. I think the number of negative complaints means this conversation is right and fundamental," she said.
Amanda continued: "What hasn't been really highlighted is we have been inundated with overwhelming positive responses, hundreds of thousands of them.
"As the BGT family, and Diversity are very much a part of that, Ashley is doing a phenomenal job as a judge, and we stand by him and stand by that performance 100 percent."
Meanwhile ITV this week issued a statement standing by the group.
They said: "Britain's Got Talent has always been an inclusive show, which showcases diversity and supports strong storytelling in all forms and ITV stands behind the decision to broadcast Diversity's performance on BGT.
"Ashley and the group are a great example of the talent, creativity and diversity of modern Britain and their performance was an authentic, heartfelt response to many of the issues and events which have affected society in 2020."
TV watchdog Ofcom has yet to say if it will be investigating any of complaints further.
Britain's Got Talent airs on ITV on Saturday nights.