At any point in time one or both of them could be married.
At any point in time one or both of them could be single.
They would be in regular communication with each other: texting, facebook, email, IM that sort of thing and not friends with the other’s spouse or partner.
They are friends so more than likely they would enjoy some of the same activities: bowling, movies, going out to dinner that sort of thing alone and not in a group setting.
And does their sexual orientation matter: if she is a lesbian but friends with a man vs a hetero single woman friends with a man.
Can a man and a woman be friends without a sexual element.