Write her a letter/email expressing this passion. If she is inclined, she will make a gesture.
I agree with georgejefferson, if she didn't review your file the first time around as a member of the adcom to begin with, and
she really does like what she sees in your materials, she can be an inside force advocating for you application. I don't think you should actually outright ask her to do anything, other than maybe review your materials becuase you would so very much like to work with her, and as for a letter of recommendation, that's totally out of the quetsion. I think your letter to her needs to be incredibly humble and succinct. On the whole though, I think this is an epsecially good idea if the law school indicates that the adcom cannot accept additional materials from WLed applicants.