you know how Lorna despises humans and tortures them?

what if instead of the humans being tortured and hated by Lorna, the ones hated by Lorna are CATS? 

im sure everyone is familiar with the common trope of cats mostly hunting mice and toying with them before they kill or eat the mouse.   
  
Like think of Lorna being born as a baby mouse in a mouse nest along with her siblings during an active housecat ambushing her mom and fellow baby mice siblings

 Lorna witnesses her mom and other mouse relatives get killed and eaten by a cat, then Lorna develops hatred towards felines and wants to exterminate them

She escapes as a baby mouse, being the only mouse survived, and roams around the urban areas until she turns into a grown mouse, and she comes across a person who "protects" mice by capturing them, feeding them, and helping them live (Hospital owner in this sense)

the hospital owner guy turns out to be a scientist who captures rodents for experiments, and does a failed experiment on Lorna, turns Lorna into the body she has.

The scientist still takes care of Lorna no matter how bratty she is acting. Lorna starts liking humans like him... or atleast somewhat more than cats.

Lorna turns 25 and she grown and able to make her own decisions and choices and decides to "work" at an animal shelter ran by humans. She cares deeply for other animals but not towards cats.

Lorna puts on a nice kid friendly personality caring towards felines when her co-workers and boss is around her

but when Lorna is told to take care of the cats in the other room, Lorna takes the cats/kittens/felines to the other room and sadistically tortures them such as gutting them, Mauling them, eating them, scratching them to death, and other ways.

They go unnoticed because Lorna says to her boss at the animal shelter "she donates the cats to other families who want them" which is to cover up how she secretly murders the cats and why they go missing. She washes her clothes when they have blood on them.

For each and every cat they tell Lorna to take care of, she is planning to kill each and every single one until there are no more cats to be taken into the animal shelter and her actions don't go noticed YET.

In my opinion this idea of Lorna and the other mice getting revenge on cats instead of humanity would be interesting

I have a good terriblemouse what if