I'm not trying to break down how what she does in order to expand her arm, that bullshit is for Oda to explain.
What she does is more than clear for me to see, if you disagree that's cool, im not trying to convince you or change your mind.
Luffy in G5 can do everything the other gears can, as they're all an offshoot of his freedom mode gear. So I'm not nitpicking G3 or 5, but that she's using his expanding arm ability herself