It looks to me like there are two different girls of the same name who were born about 2-1/2 years apart. They might turn out to be cousins. This kind of doppelganger situation is surprisingly common.
I have created a number of profiles for people like this one who resemble family members, but probably are not a family member. A separate profile reduces the chance that someone will decide to conflate the two people, and it increases the chance of figuring out who these mystery people are.
Just go to the Add tab, select New Person, and create a profile for the Annie Arnot described in the sampler, including details about her that you have from the sampler or the museum. Leave yourself on the profile as profile manager. Mark Arnot-213 as a rejected match to the new profile. Remove most of the content about this second Ann(ie) from Arndt-213, but include notes in both profiles about the apparent existence of another girl of the same name, and include a link to the other profile. And do consider taking the time to make profiles for all of the other family members included in the sampler.