Try the full OED, link is
http://www.oed.com/view/Entry/78475. If you don't have access to it then you should be able to sign in through your local library.
This definition may not be the most useful in defense of the word as it was: "Attested earlier in (often derogatory) reference to women with respect to their occupation or social status: see senses 7 and 6." These two senses are prostitution and servant work, but do not that the word often is used, not always. However, another definition is the following:
"Used as a form of address to a girl or woman. See also my girl at my adj. 2a.Often (esp. in later use) in informal contexts, implying intimacy or friendship between the speaker and the person addressed." Note woman, which contradicts the claim that there is always an age element to the word girl, and intimacy or friendship.
I would be surprised if your local librarian cannot get you access, so you (and Wolf, if reading this) can check that I haven't just made something up and attributed it to the OED. My fault, I should have made it very clear where I was quoting from, especially as this is such a charged issue.