Oh, awful.
Make sure Lucie is okay for now. I would restrict her movement till I found the source of the dog food.
Give her plenty of fresh water, then in a little while, some of her regular food, perhaps moistened. If it was big chunks of dry dog food, her throat may be scratched up.
There is a rehoming forum here on BYC, and there are animal rescue organizations looking for loving homes for ducks. It takes a little time to integrate new flock members, but it is done successfully all the time.
You might consider getting a nonbreakable mirror for her until you find a friend or friends.