People often talk about someone they like to other people or get them to talk about it. Even if they have a serious conversation in the company of colleagues, they can casually join another one as soon as they overhear a familiar name mentioned there.
Interesting detail: a person in love can speak about his object of desire in a very, very negative way, claiming to himself and others that he is barely in love. In this case, they usually say something like “Mary is a little weird!“ or ”John is such an idiot!“
One more thing. During the course of conversation, lovelorns tend to point out a similarity in interests: “It seems that the only people who watch Games of Thrones are me and Paul.”