I thought that Freundin was just the feminine of friend? Not specifically a romantic interest. Therefore in English this could be "Does your friend have a sister?", or "Does your girlfriend have a sister?", OR "Does your girl friend have a sister?". Can anyone tell me why the third option was incorrect?
What about deine Freundin? Does that usually mean girlfriend? Or just meine Freundin? That is, can someone else be talking to you about "your friend (who is a girl)"? Assume they don't know the relationship. For example, would it be fine for a cashier to say "deine Freundin" about a lady you're shopping with (perhaps she is your sister in this example), or would that sound like an assumption that you are dating?