I agree, but in the Supergirl episode she can't understand how her parents could make this weapon to defend Krypton, but would she do the same if it came down to a choice between using the weapon or the end of humanity.

Many have complained that the crossover didn't really start on Supergirl, but I seem to remember in one of the trailers for the crossover, someone (I think Felicity) said they need to kill the aliens. Kara already stated that the aliens came to Krypton and killed several people, so they may be too tough even for her.…