The actress, who now stars in US soap General Hospital, admits the hellish experience in Montreal, Canada at the beginning of her career made her mistrust all men.
She tells OK! magazine, "I had to get myself out of what could have been a premeditated rape.
"(I was) in a different country and you're all alone, and you find yourself in a situation you've heard about, but never planned for. I had to rely on myself to get out of what was truly the most horrific situation I had ever been in."
Monaco's mum flew to Canada to rescue her daughter and take her back to Los Angeles, but the trauma of her experience left her scarred for years.
She adds, "My perception of people became so jaded I didn't even trust the mailman. I had been mentally raped and violated, and I was so messed up."
The 29-year-old star admits the experience is probably what has made her value her relationship with her longtime boyfriend, who she started dating when she was just 15.