In 6x22, Mark tells Lexie that he's still in cinta with her after they break up the first time. When they get back together in season 7, Lexie tells Mark she loves him in 7x11.
And then in season 8, Lexie tells Mark she loves him outside of the hospital in 8x22. And she he tells her he loves her as she was dying in 8x24
When Mark gave the "you could have a husband" speech [underneath] he berkata "I'm still in cinta with you" but I don't think Lexie has berkata anything to him. That's as far as it goes though because I don't think he ever berkata 'I cinta you' properly. He's told Callie though I'm sure he has.