actually we also say 'girlfriends' for this - if you use it in the plural sense, it always means 女性朋友。 women use it often (again, usually in plural): "me and my girlfriends like to go out on weekends". or "A girlfriend of mine also likes this kind of lipstick". but if you want to translate 女性朋友 more clearly, unambiguously, and literally, you can say : "female friends" or "friends who are girls"

friends of the female gender lady friend(s)

Look at the sentence: "She's a friend." The "she" tells you already it's a girl! If you're a guy, a girlfriend is a girl you have sex with. If you use "girlfriend" to refer to your female friends, then it sounds gay. If you MUST specify, then you say "female friend".

女性朋友 = female friend