Singer Melanie Martinez has been accused of sex assault by a former friend, who claims she “repeatedly" refused her sexual advances.

Timothy Heller, a female Los Angeles-based aspiring singer, came forward with the allegations late Monday, sharing her story on Twitter about how she said Martinez, an artist who shot to stardom after appearing on NBC’s “The Voice,” sexually assaulted her.

“I have kept this secret for years, convincing myself that it wasn't a big deal and I wasn't hurt by it. The thought of accepting that my best friend raped me seems insane,” Heller began her post on Twitter that attracted more than 61,000 shares at the time of publication. “When faced with a friend who really needed help though, I can honestly say she let me down completely.”

Heller claims she was sexually assaulted by her then-best friend “during the most difficult time in my life, my rock bottom,” and taken advantage of during one of the nights she slept at the singer’s place.

Heller did not specify when the alleged assault occurred.

“I never said 'yes'. I said 'no', repeatedly. But she used her power over me, and broke me down,” she said. “Just so there is no confusion, I was molested by my best friend.”

After multiple attempts to touch her, Martinez proceeded to perform “oral sex on me and then I was penetrated with a sex toy without being asked,” the woman alleged. “She knew I didn't want to, I made that clear,” noting that she was “completely not reciprocating.”

Heller wrote that she was encouraged to break her silence following the recent sexual misconduct allegations against celebrities and other popular figures. “The only reason I do this now is because I'm hoping because of recent events, people will believe me.”

“I beg you to imagine her role in this being a man. Girls can rape girls. Best friends can rape best friends. Friendships does not equal consent. Silence doesn't equal consent. I wish it wasn't so hard for me to convince myself of these things,” she added.

Martinez responded to the allegations on Monday, writing on social media that although she’s “horrified” by the allegations, Heller “never said no to what we chose to do together.”

She wrote: “I am horrified and saddened by the statements and story told by Timothy Heller. What she and I shared was a close friendship … We tried to help each other. We both had pain in dealing with our individual demons … She never said no to what we chose to do together. And although we parted ways, I am sending her love and light always.”