Appearing on KIIS FM's Kyle and Jackie O Show with boyfriend Jarrod Woodgate, Keira said she started the rumour that Ali left Grant because he asked for a "threesome".
"I'm the one that started the threesome one, because I knew what actually happened and I didn't want it to come out, so I started the threesome rumours," she said.
"I told someone who I knew would talk to the tabloids to protect her. Girl code."
Once Bachelor In Paradise had finished up, Grant alleged to New Idea magazine that he and Ali actually split because she cheated on him with his best friend.
The revelation came after Jarrod slammed Ali, revealing that he thinks she will make a "boring" Bachelorette.
"She's just fairly lame and boring and I don't think she has the personality to stand up to 22 guys at a rose ceremony and make something entertaining," he said.
The couple also revealed that the first time they had sex was whilst filming Bachelor In Paradise in Fiji.
"We actually had sex for the first time was on the show, that's when we had sex," Keira admitted.
"It was the last date when you decide if you're going to be together."
