"Super-horse vanished just like krypto, streaky, and mr mxyzptlk!"
Huh? Did she "kill" mxyzptlk too or is she just bringing it up for no real reason.
She certainly wasn't being very careful though. Comet's death looked intentional ("oh, I tripped...somehow. Oops sorry super-horse") and she had to have been really careless to let her mother walk across the room and touch her.
I also like how superman seems to be rubbing it in. Harsh.