The photographer was B & G Moses of New Orleans, Louisiana. I was able to find out a bit about this photography studio which was operated by brothers Bernard and Gustave Moses, originally from Bavaria and who immigrated to New Orleans. At the time of this photo they were operating a gallery on the corner of Camp and Canal Streets. They were both intermittently active with photography work in New Orleans from 1854 until their deaths. The gallery was shut down in 1861 when the brothers joined the Confederate Army, Gustave serving as a 1st Lt in the 21st Louisiana Infantry. After the war, they revived their gallery in 1866. Gustave took his business to other parts from time to time, but always returned to New Orleans.
The young lady in this portrait is identified as Edelia Weinberg. I was never able to locate her in any census records, but I did find a New Orleans marriage record where Edelia Weinberg married Lewis H. Goldman on July 31, 1878.
The only other records I could find for this couple were their burial in the Jewish Cemetery in Monroe, Ouachita Parish, Louisiana. Edelia Weinberg Goldman was born in Castor, Bienville Parish, Louisiana on May 17, 1859 and died November 1, 1891. Lewis Goldman was born August 11, 1854 and died October 12, 1913.
Despite her somewhat portly stature (some part of that which might be petticoats) and black dress, Edelia's features are quite young and she could easily be 18 or 19 in this photo, which would date just before her marriage. In fact, it could even be the portrait of a bride, since wedding dresses at that time were very likely to be dark colors. She is wearing rings on both hands, the one on her left hand having a large stone, which could be an engagement ring. (Engagement rings weren't necessarily diamonds at that point in time.) It does not seem that there is a wedding band as well, so I am inclined to think this was the portrait of a young woman about to be married.
But I'm a romantic. So who knows?