[Kamikaze Chinchilla]

She's a slut or just doesn't realize that he's married. You really should ask him if he's ever told her that he's married.

There's nothing wrong with a husband having female friends, or vice versa. But I think this is a case of your husband being oblivious about the consequences of not being clear with his wife or his friend. I don't think he's cheating on you..just being derpy about saying anything about his personal life to his friend, unless cornered into doing it.