The pair - who are official boyfriend and girlfriend - made it to the final of this year's series.
They finished fourth in last Monday's live show having had a rough final few weeks in the villa.
While at one point the pair were favourites to win, a lie detector test amongst other things saw some brand Gabby's feelings for Marcel "fake".
It seems as though some other viewers went further, even sending Gabby threats online.
Speaking to the Daily Star, she revealed: “I couldn’t believe my phone when I came out.
“I’ve had death threats. I’ve been told to kill myself. It’s crazy.”
Chatting to the newspaper, Gabby went on to suggest that the editing may have been behind some of the hate.
She said: “Apparently there’s been scenes shown where it looked like I was being horrible to Marcel.
“I’ve been told they showed stuff like where we were having a conversation, he’d say something and I’d stick my middle finger up at him.
“It would obviously be a joke, but it would cut off before you could see that. When I came out, I was like, ‘What have people been seeing?’ You don’t know how you are being edited.”
Gabby went on to insist her feelings for Marcel were genuine and the pair were planning to stick together on the outside.
She said: “We are strong and we are going to be together.
“I could have chosen to go with someone else who came in the villa but at no point did I want to jeopardise what I have with Marcel.”
Love Island's reunion show airs this Sunday night on ITV2.