You misunderstood my point, there's no word which claims someone of an opposite gender is a friend. If you haven't noticed, "girlfriend/boyfriend" states someone you're dating. Though to claim they're friends, you wrote an entire sentence stating "she is a friend" or "he is a friend"; there are no words like "veninde" which means "female friend", instead you have to say she's a "female friend". Which are two words with different meanings, instead of one word with one meaning.
You're British, you probably only have one language or languages that don't have words with a specific meaning; so it would be hard to explain it to you.
If you were Scandinavian or another nationality, it would be easier for you to understand what I mean because you'd have something to compare English with.