Agreed.
I think ending the movie on the Bat signal alone is a stronger choice. After all, Catwoman does not answer the call of the Bat signal anyway, this is the last time she is seen in the series as a whole and leaving her fate more ambiguous is more fitting for her character. This is as she is a bit of a mystery, especially how she actually gets her “power” of nine lives etc.
Just my two cents!
Well that’s if you don’t include the new Batman 89 comic which features her.