My feeling is that this portrayel to account both charactertisation can be combined. The old Cass who thinks in symbols, and the stuff she's done. She managed to redeem herself - But Cass feels she is the wrong person to truly redeem the symbol of Batgirl in Gotham. However Cass thinks Steph may just be the right person to do this if she gets the support she needs. (This also explains the different costumes presented).