I think what she means is a military-inspired garment. Women's fashion through the ages have taken inspiration from men's clothing -- including military.

Helen, I'm no expert on 1865, but I found a few links for you. It sounds like you would wear a long skirt without a hoop crinoline. I'm not sure about the shoes. Please keep in mind, I don't know about some of these websites' accuracy and whether the information is 100% authentic:

http://www.corsetsandcrinolines.com/...p?index=186043

http://users.tinyworld.co.uk/sidesad...%20detail.html

a modern rider in that style:
http://ridingaside.blogspot.com/2009...reat-news.html

Scroll down to "outerwear":
http://en.wikipedia.org/wiki/1860s_in_fashion

I hope some of these links have helped you.