Trevor admitted to emotionally cheating on his ex-girlfriend, Sierra, on this week's episode of The Bachelor Presents: Listen to Your Heart -- but Natascha claims he also physically cheated.
Monday's episode saw Natascha enter the house ready to confront Trevor over his past with her good friend, Sierra. She claimed he was a liar and cheater, and when she questioned him about the allegations, he defended himself, saying there was no "physical cheating."
"Yes, there was some emotional cheating," he confessed to Natascha. "Yes, there was [lying]."
Natascha pushed Trevor to discuss his past with his new romantic interest, Jamie -- who has been open about being cheated on in every former relationship she's ever had. "There was some emotional cheating, and she ended up finding text messages with another girl. I didn't physically cheat, nothing happened, but it was still wrong," Trevor said. At first, Jamie had a lot to think about, as cheating was her "deal breaker," but she decided to give Trevor another shot.
In an interview with ET's Lauren Zima on Monday, Natascha opened up about why she decided to confront Trevor -- and alleged he wasn't fully honest about his behavior.
"I'm learning new things every single day. After we finished filming, things that have come out," Natascha claimed. "This is not just my girlfriend. There are so many other women he has done this to. He is a master manipulator, and it's shocking to me how many women have been caught up in his web."
"It's really upsetting and it's disappointing to see. It's sad to see these messages from women," she added.
Natascha said she didn't come into Listen to Your Heart knowing that Trevor was on the show, but once she put two and two together, she felt compelled to speak up.
"I knew that he had hurt my friend really, really badly. He had broken her heart, she was very public about it," she explained.
Natascha said she had been told by Sierra that it wasn't just "emotional cheating" that Trevor engaged in, like he admitted to.
"First of all, that's just as bad in my book, 'Oh, I've been talking to women behind my girlfriend's back.' That's just as bad as physically cheating!" she said. "He was trying to dodge a bullet there, and I could see right through it."
"I've been told it was definitely not just emotional cheating. And you can google it now," the 33-year-old pop singer told ET. "There are tons of girls coming out saying the same thing."
Jamie decided to stay with Trevor after hearing about his past, and Natascha said all she wanted was to expose the truth about Trevor, and let Jamie make her own decision.
"Being my age and going through what I've gone through in relationships, it's like, every time you can spot it sooner. You can spot that red flag sooner and that's what I did when it came to Jamie," she said. "She's a sweet girl and no one deserves this."
"I'm not here to tell her what to do. I'm just here to help guide her or give her the information that will help her make the best decision for herself," she continued. "As women, we have to look out for each other."
Natascha does, however, think Jamie was under Trevor's "spell," and while she doesn't doubt Jamie's motivations for joining the Bachelor spinoff, she's skeptical about Trevor's.
"Unfortunately, no. I don't think [he was there to find love]," she said. Natascha alleged that she's gotten "multiple" messages from women claiming to have been cheated on by Trevor. "I've gotten so many messages from women saying, 'Thank you,'" she added.
Natascha doesn't think Trevor is looking for his "one and only," but that's what she was hoping to find on Listen to Your Heart. She earned Ryan's rose on Monday night's episode. "It starts off strong between us, and we'll see where it goes," she teased.
In a recent interview with ET, Trevor said he was "blindsided" by Natascha's allegations on the show.
"It is [a big deal], but just like any other part of life, you can't control things that have happened," he shared. "All you can control is how you react. I think I was nothing but myself on this show."
"I'm proud of my journey that I've had on this show," Trevor added. See more in the video below.
The Bachelor Presents: Listen to Your Heart airs Mondays at 8 p.m. ET/PT on ABC.