Depends on your definition of "legit" :)
I for myself do the "Google test" when such a question arises: Is it possible to find real people that lived or are living today with these names as their real given names? If yes, the name obviously "exists" and I see it as legit in some sense, if not, the case is as yet undecided, of course because not even Google shows the whole world.
Shemara, Shemika and Sherece all pass this Google test, with real people turning up that have these names. Only Shemahlia fails.
I am well aware that this approach might be much too pragmatic for many people...