My miniature schnauzer has the same problem, but for some reason it usually only happens when he's out for a walk! He will go at least four times during a walk and it just gets looser each time. I asked the vet about it, and all she said was that I shouldn't give him fatty meat as a treat, to give him veggies instead.
Our other schnauzer has no problems, so there has to be something going on. We feed them medical dental formula from our vet, and yes, they do usually get a couple of small pieces of table scraps after were finished eating.
What food was she on when her stools were good? I have a 2 1/2 year old male Dobie and have been dealing with gas and soft stools his whole life. It is a nightmare, I a constantly on poop control, checking to see if it miraculously be normal and it never is. I had him on the best food and the worst food and no difference. I had a $300 test done and his pancreas was fine but seems to have a high amount of bacteria in his intestines. Even after a round or two of meds it didnt go away. Vet said it was an auto immune thing, but no definitive answer. He said to know for sure they would have to take out a piece of his intestine...The only time he didnt have gas and his stool was ok was when he at raw...but not raw meat from the butcher, I found a woman who made it at home but it was very expensive and he was akways hungry. I have also tried FreshPet Select. It is in the freezer in pet isle and he was doing pretty good, no gas, stools ok for him, but again its expensive and he is hungry. I put him on Chef Michaels and he has gained ALOT of weight...he is actually fat...110lbs at least. But it is not good enough food for him so I am back to Fresh Pet Slect...give it a try. Let me k ow if you find a food that works...our Dobes sem to have the same symptoms. ***@****
And I do definitely agree with ginger899 about the second veterinary opinion, also.
Try giving her canned pumpkin. Not the pie filling, just the straight pumpkin. Plop a big heaping tablespoonful of it on top of her other food and see what happens. If she likes it, gradually increase it to a half a cup or so, twice a day. Keep that up for a few days and assess. It's a folk remedy that has hardly ever failed for me. It may not totally cure her. You probably will still have to do some detective work to figure out what is the basic cause of the problem. But if you can at least give her some temporary relief and get the stools firmed up long enough to see what makes them loose again, you've won the battle. You can mix the pumpkin with active culture yogurt if she likes yogurt; that's even better. If she needs to gain weight, you can use sour cream instead of yogurt.
See if that works, and then we'll work on figuring out what triggers the loose stools. May I ask, did she ever have a lot of antibiotics at any time in her life? And I assume all of her stool samples have been negative? Do the stools smell especially foul, or do they just smell like normal dog poop? Is there a lot of mucus in the stools?
Trust your instincts and get a second opinion. I'm afraid I don't know enough to tell you what this might be. But it is obvious she needs some more diagnostic testing, of one kind or another. The vet just palming it off as 'allergies' doesn't quite sound right to me... (If we don't know what it is, call it an 'allergy'...? er, hello?)
You are feeding her well by the sound of it, and she doesn't seem to be acting sick from what you say, but there is something definitely wrong there. Has she been de-wormed? How often has she been wormed? It may just be possible she has had some inflammation set up by a worming medicine?