Should all these songs, for example, be modified to say “woman” to be inoffensive? Gwen Stephani needs to sing Hollaback Woman, Madonna Material Woman, Paula Abdul Forever Your Woman, Katie Perry I Kissed a Woman, Christina Aguilera What a Woman Wants, Pink Most Women, etc.? Are adult human females who use the term “girl” to describe other adult human females wrong, and in need of correction?
(Inspired by a tangent on this thread.)
No, it is not inherently offensive. Context and intent can make it offensive however.
I’m sure someone finds it offensive (some people are just touchy).
Context is king, as is pretty typical for social situations. “Girl” can be degrading, neutral, or empowering depending on context.
Sure you meant to say, context is gender-neutral monarch.
I asked a friend if her girls would be coming home for xmas. Her girls are full grown women, but they are her girls. Context.
The main context from which the notion that it’s offensive arises is the lack of parallel use of “boy” for an adult male human, so that there’s an asymmetry:
Female child: girl
Male child: boy
Female adult: girl
Male adult: man
In a patriarchal world—which privileges adulthood as well as maleness—that quickly got highlighted by feminists as politically suspicious. Fairness says if male people are men when they’re adults, it is sexist to call female adults “girls”; they should be “women” obviously. Adding to the picture is the historical fact that adult males have not always and equally been called “men” — nonwhite (especially black) males of adult age were notoriously called “boy”, and this underlines the claim that to refer to an adult by the juvenile term is disempowering and/or derogatory.
But no, not inherently offensive. One could (even as a fervent feminist) question why the male model for designating people is the one we should go with. Perhaps instead we should cease referring to anyone as a “man”, since “man” is a patriarchal political construct if ever there was one, and instead discard the insistent emphasis on age diff and go with “girls” and “boys”.
Context
Was interviewing a candidate for our group (primarily degreed professionals on a business development team). Candidate was doing extremely well throughout the day…until the end, when he asked if we could get our “girl” to call him a taxi. He was referring to one of our administrative assistants. We passed on him.
Yeah.
Imperfect rule of thumb: If used as the counterpart of “man,” it’s offensive and demeaning (or juvenilizing, if that’s a word). If used as the counterpart of “guy” (or “boy” even in reference to an adult), it isn’t.
What makes the term problematic is that, in the sexist Bad Old Days, there was often an attitude that only men were the Grown-Ups, and referring to women as “girls” was a way of keeping them in their place. I’m imagining a 1950s executive saying something like “I’ll have my girl [secretary] type that up and send it to you.” (ETA: Written before I saw Omar Little’s post directly above this one.) Of course, [sarcasm] nobody thinks that way anymore [/sarcasm], but the word isn’t entirely free of such connotations.
Since I used song titles in mocking the first idea, turnabout is fair play.
No word is inherently offensive. It takes cultural influence to deem a word offensive. It helps if people use the word to deliberately belittle other people in some way (even affectionately), but it’s not a necessary element.
If you think that using the word “girl” to indicate an adult female could be offensive, you could try promoting that idea on social media. Maybe it would catch on.
That’s really all that happens when other words become deemed offensive. The communication medium of the day is used to promote the idea.
Yes. And the “women do it too so it’s all right” argument is, and will always be, ridiculous. Women believe and regurgitate without thinking the patriarchal BS they’ve been utterly steeped in their entire lives (and raised by women who’d also been)? How shocking! I loathe the term “woke,” but it applies here. You don’t know better until you learn better. You don’t push back until you realize you have the right to push back.
So yeah, calling adult women “girls” is wrong and infantilizing and men and women need to stop using it.
I said no, but only because I mean absolutely no offense–same as if I address my peers as ‘boys’–if I apply ‘girl’ to an adult female. But yeah, context and knowing the audience’s pet peeves. Typically I go to “ladies”.
But I’m also giggling how the poll assumes female humans will always say yes. 
Please get a mod to fix your poll.
I voted “yes” because there is no “no” choice and also because it usually (but not always) is offensive. Context! It is much more likely to be offensive when used by a boy than by a woman ;).
Parallelism is definitely important here. Referring to “men” and “girls” is inappropriate, unless you are actually referring to “adult male human beings” and “non-adult female human beings”. Is it appropriate to refer to a female human being as a “girl”? Well, in that particular context, would it be appropriate to refer to a human being of the opposite sex as a “boy”? If not, don’t call a female human being a “girl”. And “boy” can also be very fraught, especially in the singular, and most especially when mixed with race. (But even between two adult white males, “Don’t mess with me, boy” is obviously dismissive at best.)
But sometimes, even in very traditional uses, “boy” is used for “adult male human being”, in an informal, often affectionate, and non-demeaning way:
“Poker night with the boys.” “C’mon boys, let’s show 'em!” “Attaboy!” “Old boys club”.
Throwing in “guys” instead of “boys” as a parallel to “girls” (or “gals”) means there are even more situations which are symmetrical. So, as is so often the case, “it depends”.
Moderator Note
Fixed.
When women are actually fully in power - like some of the female pharaohs, or a few other monarchs throughout history - they tend to keep the same title. Even if people refer to them as “queens” in day to day speech, their legal title is identical. So however Context chooses to identify, they are legally a monarch holding the position of king 
OP - I see you have added a poll, but none of your responses really describe my opinion.
I think it’s the least bad of many bad options for a one-syllable informal term for a grown female human. Dame, gal, chick, are some of the the least offensive options.
I don’t use the term myself, that said, I reserve to think of anyone who is half my age or younger as a girl or boy no matter their age, even if I don’t say so out loud.
But we do frequently refer to adult men as boys. Off the top of my head:
Good old boys (sometimes affectionately, sometimes not)
Bring the boys back home. (wanting to end a war.)
“Come on, you boys in red!” (heard at soccer games)
Boys in blue (referring to police officers)
Normally in sports a school or organization will have the boy’s team and the girl’s team, or the men’s team and the women’s team, but rarely (if ever) the men’s team and the girl’s team or the boy’s team and the women’s team.
“the boys of Pointe du Hoc” too