Dani and Jack, regarded as the ITV2 show's 'power couple', were torn apart last week when the men were sent to Casa Amor.
The twist also introduced twelve fresh islanders - including Ellie, whom Jack had dated "on and off" since 2016.
Dani became increasingly worried about whether Jack would stray - and last night's episode saw her fears reach boiling point.
The actress broke down in floods of tears when the main villa was sent a video from Casa Amor, revealing Jack and Ellie's reunion for the first time.
"It always f**ing happens to me, as soon as I’m happy with someone, something happens to me," she lamented. "It’s like I’m not allowed to be happy.
"I just knew it was too good to be true."
However, the clip concealed the fact that Jack has actually remained faithful to Ellie while staying at the second villa.
He has slept outside to avoid sharing beds with the new girls, and has even declared that he "loves" Dani.
Viewers reacted furiously to the drama, claiming producers had misled and distressed Dani - and now Ofcom is involved.
Within hours of the episode airing, 650 people had complained to the media regulator.
Now, over a day later, the complaints tally has hit a whopping 2,525 - making Love Island the most complained about TV show in two years.
Officials are considering whether or not to launch an investigation.
An Ofcom spokesperson told the BBC that the complaints are "specifically relating to Dani being shown the video of Jack".
"These will be assessed against the broadcasting code before a decision is made whether or not to investigate," they said.
Many Love Island fans vented their frustrations on social media, accusing bosses of "gaslighting" and "playing" on Dani's insecurities.
Some have even suggested the controversy raises mental health concerns.
Others have defended the show, pointing out that it's partly a game, with a £50,000 prize at stake.
"Dani is on a show notorious for throwing in surprises and people hooking up with other people," one person wrote. "She knows what she signed up for."
Host Caroline Flack has also spoken out about the controversy.
Appearing on ITV2's Aftersun show, Caroline Flack explained why the video was sent: “Because have to test relationships – that’s what we do."
Love Island 2018 continues tonight at 9PM on ITV2.