Is girlfriend wrong? In English, girls often call their female friends girlfriends. I think girlfriend should probably be added unless it is never meant as the female romantic friend and so one shouldn't risk having that association in translation.
Подруга may mean the female romantic friend, but we commonly say дівчина (girl, young lady) to mean girlfriend. "моя дівчина" always implies romantic relationship, while подруга is usually just a friend.
Yes, as Vinnfred said, it means just "friend". People use дівчина for "girlfriend", but there is a type of people who use подруга for that! :) I know several like that, they feel uncomfortable really saying Це моя дівчина ("This is my girlfriend"), so they basically say "Це моя подруга" ("She is my friend") with this sort of emphasizing intonation as if they were making air quotes :)
Okay, so I'm a little confused, does the letter 'г' make a 'g' sound or an 'h' sound? Because I thought 'г' meant 'h'?
So how come подруга has a по? Is that common in word-formation? Why not друга? Does that mean something else (I mean apart from being a declinated form of друг)?