This is a good question. I've found that as a woman, I am offered the same rates as men on loans that "advertise" their rates, such as student loans & credit cards. But if I want a great rate on a loan I am applying for through a bank (such as a car loan, etc), I have to get assertive & play the lenders against each other. For example, I bought a car a few years ago (first car purchase w/out a cosigner), and used my original offer (of 15%!) to get a lower offer for a virtually identical vehicle (9%- which isn't great, but it was my 1st big loan "alone"- no cosigner- so I took it). This sort of thing happens to me a LOT (buying computers, getting credit card agencies to lower their rates after I've been paying them off on time for years, etc.. I play one company off the other to get the best deal possible...).
After dealing with it for a while, this is my conclusion: the lenders will try and take BOTH genders for as much as they can, whenever they can. As women, we may appear to be easier "targets" to them initially (we were trained to PLAY NICE & SMILE lots, be less "assertive", etc...so they take advantage of that, more often than with men...). But if you "get assertive" on 'em, they may change their tunes quickly. I don't mean be an outright *$tch, but simply look them in they eye, state that you think you deserve a better offer (so first, make sure your credit hx reflects it), get really quiet, and watch them scramble. I know some men incapable of doing this, but I've known many more women who have problems with it.
Again, as far as "student loan rates" - mine appear to be identical to the guys I know.