A "guy's girl" is a woman who identifies herself, from the get-go, as somehow belonging to men.
The language of the term itself is possessive, as the apostrophe in "Guy's" is linguistically indicative of possession when referring to the subject: "gal."
I had no idea about this before, but having developed my closest female friendships in adulthood, I've realized: Guy's girls are tools of the patriarchy.
If you don't believe me, just ask a man to describe one for you.
They'll describe someone who is "mysterious," meaning sexy, alluring, but will also add that she is "aloof," meaning she doesn't share her feelings, and is therefore more conveniently fuckable. For who? For men, of course.
Urban Dictionary describes a guy's girl as follows:
A mix between tomboy and girly girl. Hangs out with mainly guys and has boyish interests, whether it be sports of comics, or boyish taste in films and TV. But still keeps a group of girl mates to shop with, watch chick flicks with and gossip about boys. She is usually the only girl in a group of guys. The guys talk openly in front of her and she wouldn't be out of place going to a strip club with them. A guy's girl enjoys the freedom guys have in farting, eating disgusting food and in how they discuss sex, but still likes to look and feel like a woman.
...First of all, a man wrote this. I don't even have to know that to know it.
He is describing his fantasy woman, which is of course a woman who is designed in a man's image, and the whole thing makes me want to throw a bloody tampon through his bedroom window.
Even if you asked a woman who has been dubbed a guy's gal to describe herself, she couldn't possibly have come up with this three-dimensional rom-com version of herself.
If she described herself this way, she is a victim of mind-control, and you need to shake her.
"WAKE UP BECKY! THE MEN HAVE TAKEN CONTROL OF YOUR MIND! WAKE UP!"
The definition above "allows" a woman to still have girly interests, as long as she keeps those behind the closed doors of her female friendships.
Pro-tip: It's hard to develop female friendships when you proudly go around proclaiming yourself a guy's gal.
The reason? Because society has instilled a belief in men and women that if you're a woman, you're somehow cooler, more legitimate, than other women when you can "hang with the men."
When women tell other women, "I mostly have guy friends" what they're saying is, "I'm more special than other women, so I just like, don't really relate to them, because I'm above it."
In other words, "I'm a cunt."
I refer again to the above urban dictionary quote,
"A guy's girl enjoys the freedom guys have in farting, eating disgusting food and in how they discuss sex," because those are a guy's freedoms -- not hers -- to enjoy.
I hope everyone who has ever been dubbed a guy's girl reads this and learns that you do not need to be like a guy to be fucking cool.
...And I hope you fart in agreement. Because that is your freedom to enjoy. Because you are human.