It's no good giving you an address for I am moving about. Your letter of Aug 12th reached me today. I am delighted to hear about the job. It sounds exactly the thing, sent by God, at your most need.
I will never laugh at anyone for grieving over a loved beast. I think God wants us to love Him more, not to love creatures (even animals) less. We love everything in one way too much (i.e. at the expense of our love for Him) but in another way we love everything too little. No person, animal, flower, or even pebble, has ever been loved too much - i.e. more than every one of God's works deserves. But you need not feel "like a murderer". Rather rejoice that God's law allows you to extend to Fanda that last mercy which (no doubt, quite rightly) we are forbidden to extend to suffering humans.
C.S. Lewis, Letters to an American Lady, Letter of August 18, 1956