I think this is an older photo, copied and printed on a postcard.
Of course, elderly people were inclined to be a bit behind the latest fashion, as is often seen in family group photos.
Though the lady's dress is a mixture of styles (home made?) of the late 1870s into the mid 1880s, a lady's sleeves were very tight in the 1880s, and she has chosen a sleeve more like the early 1870s. My guess is she was an active woman, and disliked the tight sleeves of the 1880s which limited movement.
The chairs are unusual, though. Has anyone seen such in other photos? That could identify the studio, I feel, and help with a date.
Regards Ada