Well now that doesn't mean anything. I mean first of all, that was a music video, she could have just done that for the sake of content. Furthermore, she could have been lesbian. But anyways, straight girls kiss all the time, that doesn't make them bi. However, in this case, it's true.
well in my opion that what I think that she was bi at that moment I understand does not mean anything but that what I think about her when she made that music viedo
She is, in fact, bisexual. She used to fantasize about women while having sex with her old boyfriend, and she had an alleged "sexual relation" with her burlesque partner, Lady Starlight. She admitted it to being bisexual in her interview with Barbara Walters, (the link is above on Oni_Kami's answer)