Ariana Grande and co-star Cynthia Erivo have been accused of having a “skinny-off” at the global premiere of Wicked. RadarOnline.com can reveal the pair have come under intense scrutiny for their slender frames at the Los Angeles event. And some fans were quick to document their concern over Grande, 31, and Erivo, 37, on social media, One wrote. “No hate, just (asking)… were they starving during the filming process of what?” Another added: “They look hungry,” a third user said, “Get these ladies a hamburger.” A seperate user commented: Are they OK?’ while another user chimed in with, “Were t…