That is so sad! I'm really sorry.
Same here, I watched my mother's two Greyhounds tear my 12 year old cat in two one night. I watched her die. It was horrifying.
My first instinct was to shy away from those dogs, I couldn't pet them or hardly even look at them, but then I got into some deep thinking about how those dogs felt at the moment. In this case, these were retired racing Greyhounds, trained to chase a white rabbit. Well, my cat was solid white. She was usually kept inside, separated from the dogs and she got out through a broken window in our garage that night. It finally hit me, they thought they were just doing what they had been trained to do their whole life.
Eventually, I forgave the dogs and to this day, one of them is still alive and I love him like I love every other dog.
In situations like these, you absolutely can't humanize the actions of the animal. Who knows what she was thinking? Give yourself plenty of time to grieve your loss. Do you have any help taking care of the dogs? Maybe you should just give yourself some space from her until you're able to forgive her? I promise, even if you don't think so right now, it can and will happen. You just need that time.