That's hard. Sorry :-( all advice I have is to find some comfort in the fact that kitty will have a loving forever home and that you did a lovely deed by looking after them.
You did a wonderful thing. Because of you it has a forever home. Something that may not have happened without you caring for it. You will forever be in it's heart.
You’re a good person. Thank you for such kind words. I am happy that she has a nice future but I’m silly enough to get attached to it so quickly. @curiosi