I can see your point. But why then, do women refer to their women friends as their "girlfriends"? Or have "Girls nights out"?

Well personally, I'm a guy and you're a girl. At a much older age to me you become a lady I guess. As I have explained to many women, the word woman is just not in my vocabulary. I say it but I have to pause to think about it first. So you might want to consider the context of the person using it. I had a neighbor in law school almost 40 years ago who got mad at me because I called her a lady. She was in her 20s and to her "lady" meant prostitute. So depending on the person you pretty much can't win, but again, try and consider the source and how they mean it is my suggestion.

As an aside, guys tend to de-adult a lot of relatnships, even amonst temsleves. I worked with some very high powered auto Union guys and I was "Ronny"and they were "Kenny" and Bobby". And "me and the boys" was a common way to describe a group action. Then again, so was "You gals" from the older guys and "you girls" from the younger ones.

I think it depends on who is doing the calling and the context in which the word is used.

Varies with the person

I like being referred to as a girl. Ma'am is the one I dislike.

To each his own.

Depends on context & intonation. Of course I tend to keep earbuds in at work to 1) avoid overhearing gossip, innuendo,
office rumor, & bs & 2) maintain a state of plausible deniability should anything untoward occur.

The women I work with, at least the more vocal ones, usually enter our lab with the greeting, "Hello, girls!" I always try to respond before they realize that there's a man in the room and add, "And Jim."

Yes, I can understand adults being offended by being called "girl." Personally though, I consider the source(s).

You’re not alone.
I’m constantly challenging my male friends on that usage. I keep telling them “they’re not girls. Are you a ‘boy’?”

As long as it's not intended to be used in a derogatory manner, I would not view it negatively at any age.

Depends on the context. "be quiet, little girl" is an insult. "You girls seem to be having fun" isn't, especially if the speaker is an old fart. I prefer "ladies" but often use "you kids" on my 30+ y/o sons and Daughter-in-law. And, as a totally irrelevant aside,most women I know call their breasts "the girls".