The actress plays Whitney Dean, who next week starts dating Tyler Moon - played by Tony Discipline.
In real life, McGarty is in a relationship with his EastEnders brother Anthony, played by Matt Lapinskas.
Meanwhile, Discipline is seeing Jacqueline Jossa, who plays Lauren Branning - Whitney's best friend.
"We didn't plan this, but you can't help who you fall in love with," McGarty told the Sunday Mirror. "I got together with Matt last August and I love absolutely everything about him. He makes me laugh and I tell him stuff I wouldn't tell anyone else.
"I completely trust him. But I suppose at the moment it is a bit like the kind of plot our writers would come up with, because I'm sort of going out with two brothers. It was a bit weird at first. But we've all brought the situation upon ourselves by falling for each other and now we just laugh about it.
"Jacqueline doesn't mind me kissing her man and Matt doesn't mind me kissing his EastEnders brother. It's just a job and the romantic scenes are all part of it."
Speaking of her real-life romance with Lapinskas, she added: "We've already spoken about moving in together, although we've decided it's a bit early. I've never felt anything like this before.
"People say it's a honeymoon period, but I really hope it lasts and that this doesn't turn out to be like an EastEnders storyline and all go wrong."
She concluded that she'd like Whitney to cheat on Tyler with Anthony so they could film scenes together.