Help! Urgent! 5 year old rescued dog peeing in the house and wont go to the bathroom outside. What do I do?

I just rescued a 5 year old foxhound about a month ago and she keeps going to the bathroom in the house. Whenever I let her outside, she could be out there all day long and still come inside and go to the bathroom in the house. Even when I take her out for a walk, she will not go. I'm on brink of giving her back to the rescue. What do I do? Need help ASAP. I really do not want to give her back, but she's destroying my house.