For women of the 19th century, hair was often cut due to illness, particularly illnesses that affected or seemed to affect the brain, like "brain fever" (more of an umbrella label for certain psychological and nervous ailments than strictly fevers originating in the brain) and measles as well as scarlet fever. This practice also encompassed some mental illnesses considered separately from brain fever. I can't speak to the specific woman depicted in the photograph (taken circa 1890) but this may explain her relatively uniform short cut rather than the shaping associated with men's haircuts. At least one medical text (John Harvey Kellogg's Home Book of Modern Medicine) prescribes this as late as 1909 for brain fevers encompassing meningitis and cerebritis. In addition to overall ease of care, this was believed to promote temperature regulation by allowing cool air to circulate freely near the scalp.

In other circumstances haircuts might be prescribed for women entering other institutional environments -- women entering some charitable institutions for former prostitutes (my source on this one is circa the 1860s, however) were required to cut their hair as a visible commitment to not returning to sex work.