A top Relativity Media executive has left the embattled company for a high-profile job at the Fox network. Fox Broadcasting Co. has appointed Courtin as EVP and Chief Marketing Officer for the network. She will oversee on-air and off-air promotion and advertising, national media, multi-platform & affiliate marketing, design and social media, reporting to Joe Earley, COO, Fox Television Group, and Fox TV Group Chairmen and CEOs, Dana Walden and Gary Newman. Fox has been…