If she is showing with different names (note - we cannot see the profiles of living people), then she has two profiles that will need to be merged.
You can only add relatives to existing profiles (that are not public) if you are on the Trusted List.
Is your sister a member? Did you create a profile for her? If she is a member, did she create a profile for herself?
It may be that the best solution would be to send an email to and explain the situation.