Yeah, the friend / girl- or boyfriend situation can be a bit tricky. Usually, when talking about the same sex Freund / Freundin means friend (gay couples would be an exception), but when talking about the opposite sex it's more girl-/boyfriend. It's not a rule, and at least in slang there are other terms used to make the situation more clear, f. ex. "Kumpel" would be buddy, or the "Freund/-in" is clarified by "Sie ist eine Gute Freundin (von mir)", meaning she is a good friend, not a girlfriend.
There may be a myriad of grammatical things at play here, but as I learned the language by listening, and not so much studying, I hesitate to delve deeper into the subject.