As much as we all love our furkids we have to remind ourselves that they do have natural instincts, which they WILL follow.

I am so sorry this happened - but don't blame yourself - no one person is responsible - it was just a really terrible accident!

I agree with the others, maybe a card / flowers or something would be a nice gesture. Then in a few months, offer again to take her out and get a new pet. (Yes I know you can never replace any loved one, but it can help to fill the void, and give the person something positive to focus on)