Oh wow, that's an email addy for Paul Laforte! I guess I should drop him an email. I imagine he would find the mirror interesting to see, and maybe he knows who the woman is. I'll report back on that! Thanks Sapphire!
I dug all through the photos of Cheyenne on that site and none seemed to match the woman on the mirror, but I may try posting the portrait on some other Native American sites to see if someone may recognize her, the way they did Wolf Robe.
I found some conflicting info on the buffalo nickel portrait, there are a variety of sources saying that the portrait on the nickel is a composite of three or four chiefs, depending on which article you're reading. Names I saw attributed to the composite were Wolf Robe, Two Guns White Calf, Two Moons and Iron Tail.
I'm really pleased to know who he is. After seeing his face all these years it is really neat to know he was a real person and to see his photograph.