It's her party and she'll cry if she wants to.Despite virtually crowd-surfing her way through Twitter's #JustinDeactivatedParty, Selena Gomez appears to be having second thoughts about taking ex-boyfriend Justin Bieber down a peg Gomez' barbs about Bieber's treatment about his fans and relationship with Sofia Richie played a part in the pop star deleting his Instagram account . So why isn't she celebrating?The singer, who also accused Bieber of cheating on her during their ill-fated romance, posted a Snapchat note expressing regret for her role in the social media drama.