Potty Trained Dog Started Peeing Indoors?

I have a 12 year old German Shepherd mix. I have had her the whole 12 years. Every time she has to go to the bathroom she will go to the back door and let us know. 2 days ago my 3 year old Yorkie went off to doggy boot camp and since then my German Shepherd started peeing randomly through out our house. At first i thought this could be a medical problem, but I'm starting to wonder if she is doing this out of a huge change with not having the Yorkie around?

She has done this once before when we moved across country and got to our new house she would pee in the bedroom. I just thought she was smelling another dog's scent, but it seems to be a pattern with big changes she starts peeing inside. What are your thoughts?

By Kim