It still entirely depends on the situation. If you know the person very well saying "hey girl" can just be a greeting. But if you don't know the person at all and just say "You there, girl." It is obviously an insult.
So don't make the world out to be black or white like that. What you say is not what you mean. Everyone knows this. Have you ever heard the term its not what you say but how you say it? This is clearly one of those situations.
So whether you like it or not getting an "it depends" answer is a part of life and communication in general. This isn't looking for a loophole, the question was flawed from the very beginning.
Context plays a part in the yes or no answer when it comes to whether or not a word is offensive.
For example, Nigger.
Does this word require context to make it not offensive currently?
Therefore, it is inherently offensive currently.
Moreover, the example you use us entirely tone based, and tone just translates so well to text, doesn't it? "You there, girl." is no more an obvious insult than "Hey girl" is a greeting. Why is this so hard to get? Why is it so hard to actually give a yes or a no answer to something? I find this practice of ALWAYS requiring a neutral answer infuriating. Especially in this case when it's not that hard to come to a conclusion on your own.
Inflection and tone ALWAYS matters. ALWAYS ALWAYS ALWAYS ALWAYS ALWAYS MATTERS! Even in the case of "nigger" the tone and inflection of your voice carries over its true meaning. Even though it has been labeled a "bad word" people still use it in their everyday life in common reference to one another This is apart of human speech, you cant just get tired of it, you use it every day with every word you say. Text as a form of communication is inherently flawed as it does not carry over the full meaning of each word of text. Have you ever seen a person use sarcasm over the internet and people just didn't get it?
Also you cant forget body language. If someone says "Hello there" it can be filled with many different meanings. Its not just a greeting, it can immediately tell someone's intentions or lack thereof.
Spoken communication with humans is immensely deep and complex. Only 7% of what you say is apart of the whole message. This is something you really have to understand. I'm sorry but you're just not allowed to find a neutral answer infuriating. If you wanted a yes or no question then you ask an incredibly specific question that can only be answered yes or no.
I wrote a very mean thousand word response because of the condescending nature of this reply and your previous reply. However, I came to realize something. No matter what I say, even if it's right, you aren't going to adjust your opinion. We'll just go around in circles where you say the same thing over and over, and I say the same thing over and over. Why should I bother? Why should I argue with the intellectual equivilant of a mule?
Here: You're totally right. I am so stupid for not putting "it depends" on there because this complex question require such a complex answer.
PS. I'd be more than happy to post the thousand word response, but I as far as I'm concerned, I'm done with this conversation, so any response would go totally ignored.
For me it certainly depends on the context, but that is the case with everything. I voted no, because the word itself is in no way demeaning and I challenge anyone to prove that it is, especially this teacher of yours. Most of the time, it seems to imply a casual or even personal nature. Saying something like "I met a girl." or even "I met a boy." implies an almost young attraction/love sort of thing. Certainly the phrase "I met a woman." can as well, but the word woman immediately puts more weight into it, something more serious. Same with "I met a man." although less so, because of the social attractiveness of the two sexes is very different.
To put it simply, girl/boy=casual, light hearted or of a youthful nature when used in a positive or even neutral context, it can also easily be used to demean someone, effectively calling them immature which I assume is what your teacher is saying. Where as woman/man implies a serious or professional nature, obviously still context related.
Tell this teacher that the term "girl" has effectively replaced "lass" and if you look at how that was used back then, it is mostly used to describe a single or available woman. If the teacher thinks being described as single or available is demeaning, he/she better be willing to explain why. Think about it though, when you call someone a girl, that is what it really means, "unmarried/available woman." You most often don't call a married woman "girl" unless you're her husband, and then the term is used as a term of affection. If anything the term "woman" is becoming demeaning in current young culture. You can see this by all the misogynist meme's call the females "woman" rather than "girl". example: "Woman best be making me a sandwich".