“It was just a bit of a casual thing and it was just this one occasion,' Elly told radio co-hosts Kyle Sandilands and Jackie "O" Henderson.
“Bec and I, we're honest people. We're not liars, and I don't think we would have forgiven ourselves if we were to go on there and just lie about s**t.”
The blonde beauty added that she would be coming clean with the other contestants during a round of "Never Have I Ever" on tonight’s group date, although it's likely they already have their suspicions.
At the time, Joe remained tight-lipped about exactly what had happened between the pair. But the Bachelorette dished further details in an interview with The Daily Telegraph.
"I was very shocked [to see him on the show]," Elly revealed. "I was speechless. I had no idea ... We had a bit of a casual romance."
Elly isn’t the only Miles’ sister who’ll be airing her dirty laundry this week. Becky, 30, is expected to open up about her infidelity – something she’s “very regretful” of.
“When I was a young lass I cheated on an ex-boyfriend,” she confessed to the shock jock.
“I know, it's horrible. And I've never, ever done that ever again. I had a lot of guilt for many years.”
Although she refrained from naming her former beau, Becky reasoned that their relationship was “toxic” and her actions were “self-sabotage.”
“In the end, I told him about it and ended it,” she said. “We go into it on the show.”
Interestingly, the defence contracting specialist recently shared that she had been cheated on in the past.
“I fell in love with this guy two months before I was leaving for a holiday," she told Woman’s Day. "He flew over and came to see us at the end of our travels and we spent about a month together."
“But when we came home, a month or two afterwards I found out through friends he was mucking around on me.”