This photo was originally posted on Redit. The claim is the photo was taken by a relative. Setting this aside I decided to take a closer look at the photo.
There are many living people in Old Town, and at the Cosmopolitan Hotel, that dress is period clothing. So the first thing to determine: Is this a real person in period clothing or a spirit person. Many people feel this is a child, but you need to remember that people in the past were much smaller than we are today. For instance: Anna Whaley of the famously haunted Whaley House was 4'8 and Thomas Whaley was 5'2.
I have personally done research work at the Cosmopolitan Hotel and did participate with the research side to straighten out fact from fiction on Ghost Adventures's visit. A lawsuit from the family descendants was avoided as a result of this research and the production company did remove untrue statements from the television show. There is very real activity at this location. I have spoken with the "Lady in Red" and you can find the video here:
I have only lightened and zoomed in on the original photo. This person does appear to wearing a Victorian or perhaps Eduardian dress.
The claimant says this photo was taken seconds after the first and no person is in the photo.
I have requested the assistance of a person who used to work at the hotel and is an expert on hats and dresses of the period. Her remarks: "Looks like a fake to me. The clothes are too fakey new...the style is jumbled."