Dreaming of my girlfriend combing her hair: Hair usually symbolizes understanding, thoughts and opinions. The dream of combing hair generally reflects relatively systematic and mature thoughts, understandings and viewpoints. Do you want your girlfriend to be more mature? Do you think your girlfriend's mind has become more mature?
Another explanation is that combing your hair also represents femininity. Do you think your girlfriend is more feminine?
A beautiful and mature girlfriend, happy and serene, is generally a manifestation of desire, or reflects your views on your girlfriend.
Good luck!