Question: Does "подруга" mean girlfriend as in "girl friend", ie a female friend, or as in "girlfriend", a romantic interest?

Doing a google image search for подруга seems to be getting matches for both types.

Answer: 
"Girlfriend" and "boyfriend" are most usually conveyed in Russian as *девушка* and *парень* (or *молодой человек*).

*Подруга* usually means "girlfriend" as well but its meaning is somewhat less suggestive of a romantic relationship than that of *девушка*.

As a male you do not call your female friend *подруга*, not without raising an eyebrow. Women, on the other hand, could refer their female friends as *моя подруга* (while using *моя девушка* would unequivocally imply romantic relationship with her).

If you want to rule out any romantic component in describing your friendship, you should use *знакомая* ("acquaintance") or *приятельница* (female equivalent of "buddy").
When the girl uses this word for another girl, it always means a female friend.
Used by man, it could have one of two values. Sometimes it's something between. But it definitely describes not-so-romantic relationships.