My 6 year old mixed breed is urinating in her sleep. She does this in streaks. Why and when should I see a vet?

My puppies did that for a few weeks, turns out that they were drinking too much too late and they weren't able to hold it all night long. So we took them out every 4 hours and pulled up the water several hours before bed and that solved it.

A 6 year old is far different from a puppy. I would get her into a vet the next time a streak starts. It could be a UTI. If she is spayed she could need hormones. We had some trouble with out 14 year old earlier this year and a capsule a week stopped the problem. Or it could be any one of a number of other problems. Any strange lumps? She could have a tumor.