Well, I don't know if it's that strange. It looks like the older profile was created by her sister, and I can imagine that on registering for this site, she didn't see that the existing profile, which is private, was her own.
And because the older profile is still private, I bet she didn't have a chance to merge, or was not informed on how to do that yet, so in my view this duplicate was sort of to be expected. Happened with a cousin of mine too.
Since the email address is not confirmed, it looks like we can't promote her to full member yet, which is what I normally do when I meet a cousin on this site.