Previously unseen footage seems to back up her claim, as she also says Bravo "worried about [her] safety" after the two had a "horrific fight."
Tinsley Mortimer left "Real Housewives of New York" midway through the season and, considering how brutal Dorinda Medley was to her when she was around, it wasn't much of a surprise she took off.
On Thursday night's reunion, host Andy Cohen asked Dorinda what her "issue" with Tinsley really was -- leading to a pretty shocking revelation and the airing of footage that was teased back in Season 11, but never shown.
"I believe half of what I hear in life and all of what I see and you guys saw just what was on the show. There was a lot of stuff with Tinsley that went on," said Dorinda, not really explaining all that much.
Mortimer, however, jumped in and told her side of the story. She said the rift in their relationship happened during a trip to Miami in Season 11, right after Tinsley and her now-fiance Scott Kluth had broken up for the first time.
"You and I got in this horrific fight that was not on camera because I had told you that Scott had generously given [Dorinda's then-boyfriend John Mahdessian] some money that you did not know about," claimed Tinsley. "You felt that betrayed, the betrayal you felt from John manifested itself into anger towards me, you took it out on me. You called John screaming."
As Dorinda denied the allegations, Mortimer said, "The producers wanted me to not stay in the house that night because you were going so crazy that they were actually worried about my safety. You turned on me that moment you found out John got that money and that is what happened."
While Medley said she "never got involved with John's finances" and "didn't know" what Tinsley was talking about, Mortimer claimed, "You called John saying don't use my friends to ask for money."
That claim was then backed up with previously unseen footage from Bravo.
RHONY Premiere Recap: Dorinda Unleashes on Tinsley -- 'You Bore Me!'
View Story"You don't run game behind my back ever," Medley was seen screaming into her phone, clearly upset. "I don't want you to talk to Scott. He's not your friend. When I say do you, don't do something, you better f--king well listen!"
LuAnn de Lesseps chimed in, saying she remembered that call happening as well.
"I have done nothing for you to hate me the way that you do," Tinsley told Dorinda. "Your jealousy, your hatred, your obsession with my relationship. Hey girl, I'm engaged, we're getting married, so you can just move on!"
The hour ended with Dorinda plainly telling Tinsley, "I'd hate your life."
The reunion will continue next Thursday on Bravo.