Unless Unk is the individual's actual surname, we generally presume that to mean Unknown; i.e. her birth surname (LNAB) is currently not known.
WikiTree guidelines say to use Unknown as the birth surname if the individual's birth surname is unknown. Variations of Unknown are against the guidelines.
The category Needs LNAB was probably added by someone working on the Unknowns Project (not sure if that is the correct project name) to add the profile to the project's list of profiles to research.
side note: How can you be a WikiTreer and not know what LNAB is? Just kidding!!