Poor Little Tilly! Whenever Tucker gets diahrrea I cook some rice and boil some chicken or hamburger to give him instead of his food. I still feed him at his regular times, just with the chicken or hamburger and rice instead of his Canidae. I have given him teeny bits of immodium a-d for diahrrea too because he has such a sensitive stomach, the littlest things can trigger diahrrea for Tucker. But Tilly sounds like she might actually be sick if she's panting and not able to hold it until outside...maybe you should call the vet.
One thing I would absolutely not do right now with her belly all upset is to start changing her dog food since that in and of itself can cause stomach upset.
I hope your poor girl feels better soon!