Cassie told the magazine she got pregnant with Arie's baby seven years ago, adding, "It didn't happen at all the way he portrayed it. At all!"
Arie made it seem like Cassie wanted nothing to do with him upon finding out about the loss of her child, but she argued, "The miscarriage was the beginning of the end, but it was a long breakup."
Lauren was the only bachelorette whom Arie was shown telling the story to while on The Bachelor. Arie's decision to share such personal details from his past was an attempt to open up Lauren more and make her feel comfortable enough to be vulnerable.
The 36-year-old pro racing driver and real estate agent from Scottsdale, AZ, had explained to Lauren at the time, "When she got pregnant, I thought to myself, 'Maybe this is meant to be,' you know? But I started to travel for racing, and that was sort of a point of contention."
Arie had continued: "I scaled back a little on racing, but it just so happened to be during the time of year when it's really busy for me. And then she called me when I was out of town, and she said, 'I lost the baby, and when you come home, I won't be here.'"
Arie wondered whether his ex-girlfriend -- a mother of two -- was "overreacting" when he got that phone call, but he said it didn't take him long to discover, "That was it. That was it for us... It was terrible."
Cassie said she was horrified to hear Arie talk about the traumatic event on national television, especially without her consent.
"It wasn't his story to tell," Cassie told Life & Style. "It's so disrespectful. It's very painful to see one of the worst experiences of my life played out on TV."
"That he would use this while cameras are rolling, with someone he barely knows, to garner sympathy, is just really sad."
Cassie claimed that she never even discussed her miscarriage with family members and close friends.
"I never even told my dad about the miscarriage," she confessed. "I have a lot of friends and family that didn't know, and The Bachelor is how they're finding out. It sucks."
Although Arie had been in this serious relationship, he has repeatedly insisted he hasn't been in love since Emily Maynard on The Bachelorette.
Lauren is still in the running for Arie's heart on The Bachelor's 22nd season along with one other bachelorette, Becca Kufrin. The finale will air as a special two-night event next week, beginning on Monday, March 5 at 8PM ET/PT.
To read spoilers about whether Lauren received Arie's final rose and whether he's still dating or engaged to his winner, click here.