You will need more info than that to locate your slave ancestor. Have you found her as free prior to the 1870 Census? Where was she located, the State and County and any other family members? What was her approx. birth year? What else do you know about your ancestor?
The Emancipation Records that I have only apply for people who were freed prior to the end of the Civil War, it does not apply to people who were freed after the general emancipation of slaves after the Civil War.