Another possobility is Pauline Cushman, she along w/ Nadine Turchin were the first women inh the US to be awarded Commisions. Paline Cushman was an honorary
Cav Major while Ms Turchin was a Colonel of Illinois Volunteers.
I have to admit that is the oddest reason for information I have ever received.
Ok I'm going to have to start seriously digging in my notes I didn't include anything more than some notes I took for a research paper and as I was parusing diaries... "A Mrs Marjorie, rode behind Sherman's Army during the Atlanta campaign carrying vital medical supplies from hospital to hospital. She killed two guerillas who waylaid her shortly after the battle of Raseca while bringing precious anestetic to a Union Hospital near Chatanooga.
The diary entries referencing her are from an Iowa
Cav Sgt. One entry mentions her as a splendid horsewoman who carries a brace of Colt pistols slung from her saddle. The other mentions her "...fine Stallion who is overly protective of her or just plain hates men." I remember getting the impression that she might have been an actress who rode the riverboats prior to the War. I don't know why.
I remember seeing the picture labeled only as "Marjorie a nurse w/ the Union Army." The Picture shows a striking woman in a
Cav Shell jacket over skirt or dress and battered forage cap. She must have been a small woman as the 1860 Colt in her hand looked enormous.
I have done a good bit of research in the Wisconsin historical society in particular as well as a half dozen other across the country. My notes are from 1991 or so and I have no idea what book the photo was in.
That's the info I have, I wish there was more.
My wife recalls reading something along the same lines so you might try your local library, and I would suggest looking into the battle of Peachtree and see if there is any mention of her.
I have only a few solid references to women in the Civil War because at the time I was doing a research paper on women warriors throughout the ages and ended up concentrating more on women of the 21st century.