My dog won't stop peeing inside the house on the couch?

We just rescued a one year old German Shepherd/Husky mix. She had no training previous to us, in fact we think they left her outside. She pees and even tried to poop on the couch (caught her on that one). She's very submissive and when we try to tell her she's bad, she just cowers over and pees more. We also think she was abused. But, does anyone know why she would feel the need to keep going to the bathroom in the house and more specifically on the couch? And are there any solutions to this? She's so scared we don't want to yell too harshly at her.