Britney Spears' one-time love rival Shar Jackson has poked fun at the pop superstar's MTV Video Music Awards disaster in a self-penned rap for a U.S. reality show. Jackson, who was pregnant with Kevin Federline's second child when he dumped her for Spears, was competing in the finals of MTV show Celebrity Rap Superstar recently when she enjoyed a laugh at the Toxic singer's expense. Performing as Shar J, Jackson showed off her own rapping skills when the show aired on Thursday (11Oct07) - by cracking, "They should have had me open up at the VMAs" during the song Let It Blow. The dig comes after Jackson, who claimed Spears had stolen her boyfriend in 2004, recently revealed she bears no ill will towards her ex, Federline, or his now-ex-wife Spears. Jackson and Playboy playmate Kendra Wilkinson, one of Hugh Hefner's three live-in girlfriends, are the finalists of Celebrity Rap Superstar. A winner will be announced this week (begs15Oct07). Jackson, a former star of TV series Moesha, is hoping to use her appearance on the show to launch her own R+B career. She has been working with Pharrell Williams on a debut album.