JoJo Siwa Defends 'Karma' Song, Explains How It Became Hers

JoJo Siwa has addressed the rumors she stole her new song from Miley Cyrus and Brit Smith ... telling TMZ she in no way swiped the single from anyone. We caught up with the 20-year-old outside Studio Siwa in Burbank, where she told us how she came…