She's gone as much as three days without eating.
That's actually okay. Dogs' wild ancestors commonly go the better part of a week without eating; the feast/famine cycle is in the dog's genes and it's not harmful for them to go a few days without eating (as long as they are healthy).
I bet that if you stopped indulging her, she would stop being so picky. As long as she's a good weight, I wouldn't worry about it--I've never known a healthy dog to starve itself to death.
Cats, on the other hand, actually can get toxic from not eating--but only if they are overweight. Once the cat's body starts using its fat stores, there is a chemical byproduct released from fat combustion that is toxic and can make a cat very sick if he loses weight too quickly.
But with dogs, especially big dogs, there is little to worry about. Dogs are naturally gourmands who will eat anything that is remotely edible (and some stuff that isn't). I firmly believe that picky eaters are made, not born--I've never had a picky dog, as I've never taught my dogs that if they hold out, they'll get better food. In fact, most of my dogs have been absolute piggies!
When I first got my Akbash Dog, he was 3 years old and a good bit overweight. The lady I got him from complained that he had no food drive, and she couldn't even find a treat that he liked.
Well, the problem wasn't a lack of food drive--the problem was one of too MUCH food. As soon as I brought him home, I put him on a diet. I was able to slim him down to a lean 130 pounds--yes, you read that right--and not only did that dog have food drive, he had ridiculous, insane food drive. He would constantly break into the chicken coop to steal eggs and chicken feed, and would gorge himself on the malted barley we feed to the livestock, even though it wasn't digestible for him at all.
In fact, he was actually rather food-aggressive (as are many livestock guardian breeds) and we had to feed him well away from any other animals. I could take anything out of his mouth, but if another dog (or even a goat or chicken) was nearby while he was eating, they'd be snarked at and driven off.
I've had puppies go through phases of inappetence, but rather than tempting them with something more appetizing, I simply waited it out. I never had a pup go much longer than a day or so without eating.
Another benefit of not having a picky dog is that you definitely know when something is wrong. If any of my dogs refuse food, I know that something is up, and if it goes on for very long, a vet visit is in order.