Could Supergirl's Newest Addition Be The Third Worldkiller?

Of course, Supergirl.tv noted Angela Zhou's Dr. Parker could also be one of the good guys working to assist the DEO in their fight against Reign and Purity. Perhaps Dr. Parker can analyze what's happening with Samantha and Julia, and clear them of their alter egos that are hellbent on destruction? Once again considering how far Supergirl is in Season 3 that doesn't appear incredibly likely when compared to the possibility that Dr. Parker is Pestilence, but it is a possibility. Its also a possibility that, given each Worldkiller has two identities, Dr. Parker could play both sides of the battle, although the DEO may not want someone capable of infecting the team so close to them.