So sorry for your loss. Please do not blame yourself, it sounds like she had a good life with you. I had a cat when I lived in Vermont (very rural area) and let her decide if she wanted to be an outdoor or indoor kitty. Well, she was definitely an outdoor kitty. I wouldn't have an outdoor cat where I live now...too many cars etc. but, I'm sure your cat loved being able to be outside rather than sit in a window daydreaming of the "serengetti" world that was just on the other side of the glass

Losing a pet is always hard...my thoughts are with you.