Bruce has visibly lost a lot of his optimism during the timeskip from BTAS to TNBA. He probably just straight up gave up on Catwoman, which I think is interesting plot-wise.
They probably couldn't do much with her either because there was a mandate for EVERY episode to give Tim Drake focus, which doesn't leave a crazy amount of room for femme fatales.
The short-haired redesign is giving a nod to the Cooke/Brubaker Catwoman comic too, which I can always appreciate.
All I'm saying is I think there were a lot of factors at play here