Wow, this is an odd one.
The lady's dress contains absolutely nothing that's dateable....there is no discernible style that I could use to point even to a decade in general. It's a strange dress, probably homemade and looks like it might be homespun as well, that just doesn't fit anywhere.
The design on the back is an odd one too but there a couple of very small elements in it that suggest late 1880s. Little fanlike designs in corners were popular in around that time period and this card shows a couple even if the general design is peculiar.
My guess, and you may get others

Cheers,
China