I thought she was one of the best of Glee: The New Class. Interesting that Grant Gustin was also on Glee. If they ever do a Flash/Supergirl crossover, there's got to be a sing off.
That was just a throw away gag (as was the Batman reference on Lois and Clark). I feel like the closest we've come (not counting Man of Steel/Dawn of Justice) to a serious implication that both co-exist was in Superman Returns.
Which happened in both a Superman and a Flash DTV. Weird how it's overused and played out already.
The explanation is sound, but if Kara is going to be a full-fledged superhero, that's another level of training that only Superman can give her. And I'm kind of tired of seeing Superman constantly abandoning people with powers like his. I know in the Silver Age comics, he kind of just dumped her off at an orphanage and only let Supergirl out as a "secret weapon", which is kind of messed up, but what's with this new trend of ditching fellow Kryptonians on all these DC TV shows? He avoided Superboy like the plague on Young Justice and even on Krypto the Superdog, he just leaves Krypto to some random family in Metropolis.
Or "Lex Luthor" or "Lana Lang" or "The Planet Winath" or "Mr. Mxyzptlk" or...