'Bachelor' Alum Bekah Martinez Warns That Arie Luyendyk Jr. Will 'Certainly' Cheat on New Fiancee

Bekah Martinez doesn't have high hopes for Arie Luyendyk Jr. and Lauren Burnham's relationship.

The former Bachelor contestant has been open about her feelings toward her ex after he proposed to friend Becca Kufrin, then dumped her on national TV to propose again, this time to Lauren.

Bekah has since called him a "f—ing tool" on Twitter, and revealed that he messaged her on Instagram after filming had wrapped up.

And now, she's coming for his ability to stay faithful to his future wife.

"I just think that even if they were to stay together for the rest of their lives, I think he would certainly cheat on her — without a doubt," Bekah told Access Hollywood after the dramatic breakup.

Adding, "I can't speak for Lauren, but I don't that Arie is capable of having a monogamous, serious relationship. I really don't think that he's mature enough to handle a real, committed relationship. He's impulsive and he doesn't think through his actions."

The 23-year-old also shared her thoughts on how Arie dealt with situation on Monday. She said that even with "producer pressure," Arie should not have broken up with Becca on camera.

"The way he handled those interactions with Becca was so manipulative," Bekah said. "I thought it was really emotionally manipulative. He wanted to see her break down I think, or he wanted something from her and he was not looking out for her feelings. He was looking for his own sense of well-being."

The 36-year-old race car driver defended his actions Wednesday on Live with Kelly and Ryan.

"Through every breakup, there's always questions of what went wrong," he replied. "And I knew that if we did it on camera, I could take ownership of it and that it was completely my fault and my doing. I thought that was important."

"And the whole thing started on camera, and I wanted the story to be told all the way to the end," Luyendyk continued.

But regardless of what he intended, Becca wasn't left with such a good taste in her mouth about the breakup's handling.

"It was embarrassing the way he broke up with me with the full cameras and crew around. There was a better and more tactful way to do it" she told PEOPLE Tuesday. "A breakup is hard enough, and to have it all filmed and have to re-watch it and know that people all across the country are watching you get your heart broken, it is embarrassing. It's not fun. I wouldn't wish it on my worst enemy. It was like a slap in the face."

She's getting a pretty sweet consolation prize, however — a starring role in The Bachelorette this season, which started with a partial preview on Tuesday.

The Bachelorette returns to ABC on May 28.

Photo credit: ABC