Viewers of the ITV2 reality series were shocked when she shared a kiss with new girl Katie Salmon, following their date during last night's (3 July) episode.
However, there was no-one more stunned than Tom, who could only watch on at home as his girlfriend kissed another woman.
Taking to Twitter as the show aired, he made his feelings on the matter very clear:
Tom had been in an on-off relationship with Sophie before his elimination from 'Love Island' last week, and since his exit, he's insisted they could make it work on the outside, despite their ups and downs in the villa.
However, Katie set her sights on Sophie as soon as she arrived on the Island last week, admitting that she wasn't bothered about her and Tom's history.
She said in the Beach Hut: “She has said that I’m her type, but I’d like to get to know her before I start jumping into things. Like I say, it’s early days with her and Tom. Obviously I might have limited time in here, so I have to move quite quickly. But you can’t move too quickly because you can’t look too desperate, so you’ve got to play it cool.”
'Love Island' continues tonight at 9pm on ITV2.
Tap the image below to launch the slideshow...