@Arrowverse lover331 kara zor-el is not the only supergirl in the DCU there have been others like cir-el, matrix, kara zor-L, Lara and many others throughout the multiverse
And also; the arrowverse has a seprate cannon from the DCU they do share some similarities but they are not exactly identical so be aware that just watching the shows won't give you knowledge on everything related to supergirl and rest of the superman family