Not trying to play devil's advocate, there isn't any real excuse for what she did, but this might come down to education. The amount of people I meet who think of fish as little more than swimming potatoes, the amount of vegetarians who eat fish because in there mind fish don't have the intelligence to suffer. At the moment there is very little agreement as to the welfare standards for fish. In her mind what she did might not be any different to killing someones favourite plant.
She may have had that outlook on fish. But to me that is still very evil to kill anything(even a plant) that you know someone loves.
Example: My sister had a baby pine tree she had been growing for a year. She loved this little tree the way anyone would love a pet. After an argument with her soon to be ex husband, he smashed the tree obviously killing it. He did this because he knew she loved it and wanted to cause her pain.
It’s that sort of revenge or acting out of anger that is scary. Killing something to cause someone else pain.
I am aware that this could come down to education or parenting...
But I think those are also lame excuses for people to use as justification for their actions. You know what will cause someone else emotional pain, that’s why you choose the action that will hurt them when getting revenge. That’s also why laws are in place for times like this. It is not only morally wrong to kill things it’s also legally wrong.
She knew she was doing something horrible bad, she just didn’t care.
My two cents anyway. Sorry for the long rant. Lol