I leave food out all the time , butter for one, it rarely goes in the fridge because it becomes too hard to spread easily. Also, sometimes, I'll leave a small home baked loaf of bread out, or a bag of potato chips, etc. There are other times, when I bring in groceries, I have to make several trips, and put food on the table that cannot be put away immediately because I have other food sitting in a hot car that needs brought in.
Also anyone while preparing dinner and setting out food can get distracted or have to leave the kitchen for a few minutes -- I live alone, but sometimes invite people over dinner. I don't have a way to close my kitchen off to the dogs, if say I need to go use the bathroom, or I want to go change into some nicer clothes before my company arrives. So, saying that leaving food out is a people training issue and that it's not right to make a dog fight it's base nature is kind of off the mark.
Notahusky, as far as solving the problem, I'm not a dog trainer, but if he were mine, I would try these things. I would refresh her basic training, if I kind of let it slack, or if I had a dog that never had any...and I have adopted dogs like that.
Get the 'sit and stay' down, and get her use to obeying commands, listening to you.
Once she's obeying your commands, for the basic stuff, teach her to 'leave it' when it comes to food on the floor, even at feeding time, until you give the signal that she can have whatever is laying there, be it a doggy biscuit or a toy. Also absolutely ban her from the kitchen, never allow her in there.
There are some videos listed in this training forum, in the sticky area...which show you some methods on the leave it command. I am absolutely terrible at remembering names, so I hope one of the other posters will come in and tell you the name, but there is a highly recommended YouTube trainer who I *think* goes by the name of Kiko, or something like that. I believe I watched one of her videos a long time ago on how to teach a dog to 'leave it'.
Now I don't know if that kind of training, will carry over to a point where a dog would leave food on a counter alone, especially with one who's already experienced the joy of counter surfing for food. But it might be worth a try.
I've only had a few incidents where I've lost food that was on the counter, and that was just with 1 dog too. She didn't do it 99 percent of the time, and in the course of 16 years of owning her, I lost 1 birthday cake, an opened can of cat food, and a cooked smoked-duck that was cooling off after being cooked.
None of my other pets, even adult ones that I adopted, never stole food from off the counters or table. Nor did they raid the kitchen trash can. Oh, the can of cat food. I use to feed my cat on my clothes washer, 1/2 a can mixed with dry. She didn't like cold canned cat food, so I would leave the unopened can on my kitchen counter with the lid over what was left and a paper towel over that so flies couldn't land on the can. I would come home for lunch some 3 hours later and feed her the rest of the food out of the can. That cat outlived two of my dogs, and I had two other dogs afterwards, and none of them took those cans off my counter...and I'm sure they could smell the opened cans. The one dog I had, Hey You, who did on very rare occasions steal things... she did it so rarely that I was always shocked by it...but she never got worse, in knowing she could get up there and get things if she wanted too, so I never did anything about her once every 5 or 6 years food thefts.
I also pretty much kept my dogs out of the kitchen, especially when I'm cooking and I don't feed them while I'm at the table which is right at the line where the kitchen ends and the living area begins.
Hopefully someone here can give you some training methods to use based on personal experience in having a dog that does something like that, or point out the name of that YouTube trainer, that I can't recall. :P
In the end, you might have to always food proof your kitchen as SageCityClev suggested, and be diligent about the dog being around when there are times you have food out, but hopefully, your dog can be re-trained to leave things alone, no matter how tempting.