Killer Cat

The lovely Big Feet, now aged at least 13, recently, ostensibly treated for arthritis by the vet, although I suspected a pulled muscle, has shown improved action in the field, so to speak!  I don't know why but she has become more grumpy, more vocal, insisting she goes out or insisting she stays in.  She cries in a way that she didn't in her previous home (not that I was aware of), for food, or to be let out or to be let in!  She likes people. She likes company. She is a talkative cat. She likes affection. She gets affection. We talk to each other.
BUT... RECENTLY...she has returned to her younger youthfulness and become KILLER CAT!
This cat used to be a moler if she could be bothered! She used to trot across a busy road to the pedestrian pavement of the bridge, cross the road again and go to the English Common by the riverside, return the same way with a large, LARGE, rabbit or baby rabbit and proceed to be proud of her display!  Or go in the other direction to a garden to remove moles. The owner was very happy!
RECENTLY, the mouse population outside this house has been decimated by at least one a day. Not shrews, but mice, and I am convinced that at least one was a harvest mouse, so I was upset.
Cats kill and I know that!  BUT THIS CAT IS GAINING WEIGHT!!
I was distraught when I heard what I cheerfully thought were baby birds squabbling in the courtyard but to my dismay it was BIG FEET in Le Grand Salon batting an 'Eurasian Blue-tit' fighting for its life.  Poor wee thing!  Knowing that it had little chance of survival it was taken outside, set on the rockery to draw breath, but to no avail!
I am searching my conscience as to why I am upset when she kills a swallow, or a harvest mouse, or a blue-tit, or bat but am not emotionally straught, yes I mean this word, when it is a shrew... although I have rescued those in my time and been bitten in the process!
Imagine what it would be like if a HUGE GIANT CAME AND ATTACKED US... if a dino-saw-us!
I would faint! I would be DEAD!
 with thanks to Wikipedia photo usage!