6 year old female urinating inside

Question
My dog is a mix breed, border collie, Maltese, shiz tu (spelling) and weighs 29 pounds, she has recently been to the vet for a belly problem from getting into the garbage, which is usually kept on the back porch when we are not at home, missed one day and BAM she got it. Anyway, we have a neighbor who has a male dog that has "piddled" on my floor one time. I cleaned it with vinegar, pet stain/order remover etc, and have removed the carpet that was in the room, however, my dog, has just recently, been peeing on that spot on the hardwood floor, she is also in heat. and has not been fixed, that is coming this month. What could be causing this? She doesn't do it during the day, no matter how long she is left alone, only at night when we are sleeping? Any suggestions? Thank

Answer
It's hard to say, Mindy. Are you sure that it's urine and not bile that she's throwing up during the night? They look very similar. If it's urine, it could be that she is still smelling the odor of the urine that is already in the floor. What if you block her access to that room at night?