The confession came in a segment called "Excess Baggage".
Co-star Adam Farrugia was the one who read the disclosure out loud.
"This girl once hid cockroaches in her boyfriend's breakfast when she caught him lying," Adam read.
When he named the girl as Vanessa, she got a round of applause from the other contestants.
"Don't take any breakfast from Vanessa," Adam said.
"I won't be eating any cereal in the kitchen anymore, put it that way," another said.
One thing we'd love to know is whether or not this 'lying' ex was Jessika Power's brother Rhyce Power.
Since Jessika Power has a literal petition to get onto Love Island to get revenge on her brother's ex, we wouldn't be surprised if it was him!
"She slagged me off on social media and when the promo for Love Island came out, I thought, 'oh no, that's why the social-climbing has been happening,'" Jessika revealed on KISS FM's The Kyle and Jackie O Show. "She said a lot of things about me so why not say it on air."
Jess hasn't ever approved of Vanessa, admitting that she told her brother from day one that "she's trouble" and he "needed to get rid of her".
It doesn't help that Vanessa actually dated Jessika's ex-boyfriend Dan Webb from MAFS.
SO MUCH DRAMA.
"She dated my brother and then she went to Dan and one of my other ex-boyfriends," Jess continued, angrily. "They were only together for a few months but then she went to my ex Stephen. I was confused and shocked."
So, will Jess make it on Love Island?
“If you've seen the Season 2 Islanders and already have your eye on someone then it's the perfect time to apply — there could be a spot in the Villa that only you can fill.”
“If you are sexy, young and single, aged 18-35, and are warm, honest, open and truly looking for love, then follow the link to apply for Love Island Australia."
Well, a blonde bombshell who has a knack for good ratings with a mission of revenge is the perfect contender!
Maybe she will nab Vaness's partner Matthew Zukowski as payback.
WATCH: Jess Power wants to go on Love Island to confront Vanessa Sierra