Former “The Voice” contestant Melanie Martinez has been accused of sexually assaulting her friend. Timothy Heller, an aspiring singer, wrote her allegations on Twitter against Martinez, who she described as her former “best friend” who took her in. “I felt like I owed her my life,” she wrote. Heller accused Martinez, who rose to stardom after she was a contestant on season three of “The Voice,” of being manipulative and selfish, always making things about her even when Heller was at “rock bottom.” “Her power and control over me grew and grew into me having a very hard time saying...