The more time I spend with this portrait the more I love it, and love her-- a bit of a homely woman, perhaps, who doesn't look especially glad to be having her portrait painted, but such is clearly part of her lot in life as a woman of means, and she looks as if used to enduring things she doesn't especially like! 1820s-30s would be my guess based especially on her cape, bodice and hair style, beautifully housed in what I might guess is her original frame. 

8 5/16” x 7 9/16” x 3/4”; sight 5 1/4” x 4 3/4”. Very good condition, behind glass, with a bit of glare caught in photos.