Start right back from the beginning like she is a wee puppy. Your pup is not house trained yet, and something has gone very wrong with her training.
What is her schedule like? How often are you taking her outside? How often are you feeding her? When is her last meal for the day? When is her last pee/poop for the night before bed?
Is she crated? If not, buy a crate and start teaching her to be in it.
Has she been wormed? What food is she fed? Sometimes worms and/or a food heavy in grains will make them poop much more often.
Start taking her out every 2 hours...and praise when she goes. I suspect she is given the run of the house and is using your home as her latrine....too much freedom for such a young dog.
Gina