oldrags:

Carte-de-visite photograph by Maull & Co, 1864 London, Manchester Art Gallery

Full length studio portrait of a woman in mourning sitting beside a table. She is wearing a day dress, skirt has an embroidered pattern set at regular intervals, patterned band runs around skirt just below the knee, large lace net hem with scalloped edging, bodice has similar patterned band across the shoulders and bust, upper part of the bodice is quilted with vertical strips, patterned band also runs down the trumpet sleeves, white undersleeves, white lace collar, she has a black lace shawl over one arm. Drawing room backdrop with drape.

So this is the one XD Sorry again 😉  I can’t see anything that directly says she is in mourning. Except maybe the black fan? But I don’t think there was anything particular at this time that limited black fans to mourning- black fans seem to be seen in fashion plates of the next era anyway. Also it’s hard to tell what material it is- if lace it could easily be fashion, if crape well we know what that menas 😉
It may be that the gown is mauve and the museum knows this but hasn’t shared? Even then there is a fashion plate for lilac silk under black lace from only a few years later so… there may be some clues in her jewellery that can’t be seen in the scan? I’d expect her to have a headdress though if she was married and in mourning for any family member (at this time anyway).
http://www.manchestergalleries.org/the-collections/search-the-collection/

If you search for mourning and select only works with images there are a lot of cartes that show women in dark clothing. Some of which are clearly mourning (crape!) and some which may or may not be given the fashion that came and went for married women to wear caps regardless of age- also in mourning and post mourning. Given that very dark clothes were considered the most suitable for those without a lot of discretionary income (blue serge for everything!) it is usually the materials and accessories that are more easily read. Here though, I really am struggling to figure out just on the image alone. Again, there may have been a box labeled “women in mourning” before being sorted by the museum?