One would think that Melissa Benoist would be a little annoyed that Ruby Rose gets to be Batwoman, while she has to be Supergirl. Granted, Supergirl started when Benoist was in her mid-20's, while Ruby Rose is 33 starting Batwoman.
At some point, if Supergirl stayed on the air long enough, do you think they would change it to Superwoman? Just for argument's sake, if Benoist was 40 years old, would she still want to be called Supergirl?
Or is it just a DC licensing thing?