The singer was overwhelmed upon hearing Goodbye - the first track her bandmates released after she quit the pop group in 1998 - in upcoming production Viva Forever!, which incorporates the Spice Girls' greatest hits.
Appearing on U.K. talk show Alan Carr: Chatty Man with bandmate Melanie Chisholm, Halliwell says, "I started crying when she sang Goodbye, because I think it's about me. And I went (to my bandmates), 'I'm really sorry!'"
Chisholm joked, "'I think it's about me?' Yes, it's about you!", before adding, "A lot of our songs were really personal to us. Some of them are about you (Halliwell) or me..."
Viva Forever!, written by comedienne Jennifer Saunders, previews in London from 27 November (12) before its official opening next month (Dec12).