It was used, but still rare. It was also used by
German Jews. But I never encountered a form of
Rebecca that was only slightly similar to Rabea. The most common
German forms (Besides spelling variations like
Rebecka or
Rebekka) are Becki, Beke, Beeke etc., the main Yiddish variants are
Rivka or
Rifka.
One needs to explain the vowel "a" in the first syllable (in
German it is distinct from "e" and not just a spelling variant), and the addition of the final -a to an already feminine name.
--elbowin