House Trained Dog Peeing Inside?

I have a 2 year old Boston/Yorkie. She is house broken, she goes outside and uses a pad in the house. We got new sheets, they are animal print, and she peed on them the first night we got them. We cleaned it up and she did it again, so we took the sheets off and put our old ones on. She didn't pee on them.

Then we put the animal print sheets back on and she peed on them again. And this is the first time since she was like 2 months old that she peed on our bed and that is where she sleeps every night. And when we took those sheets off and put the other sheets on again she didn't pee.

Also, I noticed today that there was a wet spot on our couch and she has never peed on the couch before. I am not sure if she threw up and tried to clean it up herself or peed. It wasn't a big spot, but wasn't small either. She is drinking fine, eating fine, and playing and acting herself. She doesn't seem to have a fever. What could be causing this and is this normal?

By Debbie M.