Re: are there any other rAbertas out there?
I would have thought that there might be others who might have slightly altered the spelling of "Raberta" the way your parents had, but it does appear to be an extremely rare name in the United States at least.
If there had been any Rapertas named in the entire U.S.A. in the years 2000 and 1999, there would have had to be 4 or less, according to the Social Security Administration.
-- Nanaea