As a non-native English user, I sometimes have difficulty determining when someone mention "girl friend" really means girlfriend in a romantic relationship. Related post in ELU Does “girlfriend” or “boyfriend” always indicate partnership?
There seems to be no consensus to help differentiate the two meaning, especially in non-written interaction, except depending on the context. Of course, if the context is available.
In written communication where no previous context is available how can one tell when someone really means girl friend? What strategy that can be applied to subtly derive the information without making the situation awkward?
Ideally, the method should also cover email and snail-mail, where the exchange of information is not instantaneous and requires time; so the "clarity" of the relationship will be revealed in just one reply.
Note: I'm making up a habit to write "girl friend" when I do mean a girl friend. I never noticed anyone else using this style constantly, though.