Welcome from out in Oregon, rather iced in at present! (This is our third nasry ice storm of the year.)
I'm also a female civilian reenactor, and here are some items I have found indispensable:
Elizabeth Stewart Clark's
http://www.thesewingacademy.com Her book,
The Dressmaker's Guide, is my "bible" for both how to dress and for mid-19th century sewing techniques (some of which are better, faster, and more durable than those of modern times). It's available from her website and covers the years 1840-1865. Sign up for her "Sewing Academy Forum" which has been an invaluable help to me, especially in fabric selection. Her "Compendium" section contains a number of excellent free articles.
Juanita Leisch'
Who Wore What? Women's Wear 1861-1865 is an excellent guide to Civil War era women's clothing, based on her study and anlysis of thousands of
cartes de visite from the period.
https://www.amazon.com/dp/0939631814/?tag=civilwartalkc-20. This book gives you a good idea of the typical women's wear of the period, as opposed to the idealized fantasies in
Godey's Lady's Book and
Peterson's Magazine.
Other useful sources include Carolann Schmitt, of Genteel Arts Academy in Gettysburg, and Kay Gnagy of "Originals by Kay." If you can attend any workshops featuring these ladies or Elizabeth Stewart Clark, be sure to do so! "Originals by Kay" is an excellent source for accurate ready-made garments, particularly corsets (which are made to your measure).
Any journals and letters of Civil War women are useful--Union or Confederate, depending on which side you're reenacting. I am with a Union group (which also reenacts an actual Oregon infantry regiment at Fort Vancouver), so my bias is in that direction. My favorite (and inspiration and avatar) is Mary Livermore's
My Story of the War, about her work with the US Sanitary Commission. Mary Phinney von Ohlnhausen's journals and letters, compiled by her nephew as
Adventures of an Army Nurse in Two Wars, are available online at
https://ia801400.us.archive.org/23/items/armynurse00olnhrich/armynurse00olnhrich.pdf; they are rather different from the TV program "Mercy Street." (Note that there are a lot of blank pages at the beginning; you have to scroll down what seems like forever to even reach the title page.)