Having lost my Emily to a horrible accident, I can understand what you're going through. It's terrible to EVER lose a beloved friend, but when you feel like it was partly your fault, it seems doubly hard. Not only are you mourning your pet, you're spending a lot of energy being angry with yourself, too.
It's been over a year since Em died, and I still play the 'What If' game, as I know you're doing. I wish I had a magic word that could take your pain away, but all I can say is that Iberia was loved, and is loved, and you know in your heart that HE doesn't blame you, and you shouldn't blame you, either.
Hang in there.