I've had a stroke of luck - I've come across a complete copy of the photo from which this was evidently taken, and I've attached it below.
The photographer was in Otley, WRY, which helps me narrow it down to almost certainly one of two women, whose dates are 1798-1861 and 1800-1873. I've found references to him working in Otley between 1857 and 1870, but he may have operated outside this timespan as well, and it doesn't really help me choose between the women anyway.
I think the one born 1800 is more likely, partly because my link to her is via her daughter, and I think it's more likely to be a woman's locket than a man's, and partly because I think the photo may date from after 1861. However, I'm open to other opinions.
Arthur