Gosh, poor thing. I'd be calling your vet Monday to see if you need to bring her back. Is the dose okay? It should be 2.3-4.5mg/pound, once a day - so, it's not remarkably more than that, is it? Simplicef treats both gram+/gram- bacteria (which is good, it treats a lot) - and is used for skin, resp. infections, UTIs, ear stuff and other things - so it's for the UTI.
But this level of diarrhea is kind of extreme. Maybe double check the dosage. Give pumpkin. Also, give some low-fat plain or vanilla yogurt - good for her digestive tract.
And, bummer about the carpet - try not to get too upset at her though, bc remember that dogs have a *very* short digestive tract - so when they have diarrhea, they really have almost no warning and can't get to the right spot to go. Hang in there, she'll get better.
