I can't find any evidence for RACHAEL
in the bible. In the Hebrew bible it's RAKHEL, same in the Greek Translation, and RAHEL
in the Latin version. I don't know about older English translations or maybe French or maybe adaptions to literature.
But I assume the E slipped in, just because it looked fanciful and would still be pronounced the same way. Or as you say, to make it look like MICHAEL
. But here of course the EL part means something: "God", or in the case of YAEL
it's part of the vocabulary word.