I agree dogs and carpet... they just can't resist.
Maybe she is so excited when you get home she can't hold it?
Also some dogs do it when they are nervious?
I would check with the vet to be sure....
also remember she still very much has "puppy brain" I know it can be frustrating but it won't last forever! Keep consistant, get her checked by the vet, and have a good snuggle!
Let us know how it goes!