Halliwell sat in the audience with bandmates Emma Bunton, Victoria Beckham and Melanie Chisholm for the final results show where Mel B was voted runner-up in second place.
Brazilian racing driver Helio Castroneves won the celebrity dance contest on Tuesday night, but Halliwell insisted that Brown was "still a winner".
She said: "As you probably know, Mel B was in the live final of Dancing With The Stars and we surprised her on Monday down at the show. She was so shocked; it's the first time we've ever seen her quiet!
"She was with us in rehearsals yesterday morning and then went to the studio in evening for the results show. She so should have won… I'm very disappointed. But we are all so incredibly proud of her. You're a winner to us Mel!"