The 24-year-old actress was quietly dating Sebastian Stan, who played Carter Baizen and is a friend of her co-star Chace Crawford.
But Meester says she was left heartbroken when she recently broke up with the 27-year-old Romanian.
'When you have to resolve not to speak to someone anymore - somebody that you see every day - it's like they died,' the actress tells Seventeen.
Asked by the US magazine why her relationship with Stan was special, she says: 'I've never really liked anybody before.
'Even when I would date guys, it would sort of be on the surface and it was always a relief when we broke up.
'I've only had one experience where it was really hard and I was really sad when it ended, but that's what taught me a lot about myself and love and life - and that's good.'