Considering that Ray is a incomplete "vampire" robot that absorbs other robots in order to survive, it could be that Ray is neither male nor female.
Besides that, I do believe that a homonym of "Ray" is "Rei", which means zero in Japanese. And I do recall that Rei has been used as a girl's name, which is likely why the wiki refers to "Ray" as a girl...
Also, I do wonder something about this new character: who created Ray, and why was Ray left unfinished?
Part of me wants to believe that Ray was not created by any human scientist, but is in fact a sort of being created from the Xel itself, made from thousands upon thousands of robots made from the stuff. In other words, a mind hive taking the form of a robot, complete with a "We are Legion" sort of vibe...
Whether it happens that way or not, it's still well worth noting that Ray being a "vampire" robot is an interesting notion as a rival, although whether or not they can do it right is another matter entirely...