Catwoman's "sorrow" over the Ice Princess's death

[KeatonisBatman]

I think also that Catwoman had a plan (as did Penguin) and killing the Ice Princess wasn't part of that plan.  You can kinda see the look on Catwoman's face like "uh-oh what has Penguin done" sorta thing.

[Catbat]

Good question - was Catwoman troubled by the Ice Princess' death?
I personally think so, since she had decided to take part in the Pernguin's plan only as a way to punish Batman for having stopped her destructive rampage the previous night. My idea is that she only wanted to destroy Batman's integrity in the public eye by making him appear as a kidnapper, but she didn't want the Ice Princess to die to achieve that goal. I guess she somehow saw her dying the same way she did (by falling from a building)  and realized she had taken part in a gratuitous crime – her reaction is subtly shown as she looks down Gotham Plaza in chaos after the killing.
As a matter of fact, Catwoman wanted to play a part in the set up of Batman only to have a chance to meet him again and teach him a lesson (a purpose she fulfilled by fighting him when he tried to free the Ice Princess). Also the fact that she later immobilized the enfeebled Batman to seduce/injure him again is a hint of the fact that her main intent was to inflict him a humiliating defeat and make him lose time while the police was already on his tracks, so the trap was only functional to her plan to exact revenge on him and didn't need an actual murder.
In fact, the Penguin's plan had served her a weakened Batman she hoped to further discipline  and she didn't think about the consequences when she saw the opportunity to make that circumstance come true. My feeling is that, when she suddenly stabbed Batman's chest with her claws her idea was probably to keep piercing the batsuit with repeated thrusts while she was straddling him, so that he could have not been able to protect himself and would have soon been too exhausted even to flee  – at that point, Catwoman would have left him to the incoming policemen and completed the framing.
Since things didn't go that way, Catwoman could witness the enormity of the crime she took part in, thus her sorrow for the Ice Princess...