What is a more common and natural compliment, "Your something is..." or "You have..."? For example "You have really nice hair" or "Your hair is really nice"? The issue is that I sent a message to girl "Your hair is really nice" and she corrected me having sent me "You have really nice hair". I am just confused.
Tell her whatever she wants to hear.
In practical purposes, you are complimenting either the entire person:
You have really nice hair.
Or you are complimenting an attribute:
Your hair is really nice.
There are contexts when one or the other will serve you better.