In the movie "The Dark Knight" (2008) by Christopher Nolan, the character Joker, at a certain point, interrupts a party where there's Rachel Dawes (former girlfriend of Bruce Wayne). When he meets her he says
Well hello, beautiful!
I was reflecting on the correctness of this expression. beautiful is an adjective and is being used either as a noun or the expression "hello, beautiful" is actually a short version of an expression like "hello, beautiful girl". The second option seems to make more sense to me. I suppose this is a common expression or at least not a weird expression for a native speaker to hear.
Meanwhile, I've been using the expression "hi beauty" or "hello beauty" when meeting a girl with whom I have a lot of confidence and which I find very beautiful, i.e. a girl which is considered the "beauty" by definition, or the most beautiful girl. Clearly, this is a compliment and a greeting at the same time.
My question are:
How do you interpret the expression "hi beautiful" in the context I mentioned above?
Does it sound weird for a native speaker to hear the expression I've been using "hi beauty"?
Depending on the interpretation of the meaning of the expression "hi beautiful", this expression may mean the same or similar thing (or not) of "hi beauty", provided this last expression isn't just my invention. How different are the expressions "hi beautiful" and "hi beauty" and when can they be used, in your "opinion"?