Well, I was typing and my post just disappeared so if this is a duplicate response I apologize.
To clarify a few things, the vet's office did want me to come in but as I talked to them about what had happened I remembered something similar with a male dobe I had. I decided not to take her in but the vet's office encouraged me to keep an eye on her and not wait.
The male dobe I had was a rescue with separation anxiety and he'd lift his leg every time you left. He was tested for everything and the doc said he just had "issues between the ears" and even Puppy Prozac didn't help. He had been abused so I just figured he got scared when I would leave. I just had to make sure he was caged before I would leave.
Ladybug went home Monday and there were no further incidents from either dog at either home. Monday night I made Lexi stay in her cage but last night I let her up on the guest bed with me - under a bunch of towels - and nothing happened. I find it hard to believe if this is a medical issue it would just start and stop. I think the trianer had a point but I also find it a lot of urine for just marking.
Lexi has her annual physical and shots in a few months and I'll continue to keep a close eye on her to see if anything changes.
She has exhibited other behavior in the last few months that is different, too. I once left her loose in the house for a about 6 hours and came home to find a puddle in the hallway. She had been loose before and could hold it. She also took to chasing and eating rabbits this winter and I had her tested for parasites and checked by the vet. He said it was very natural for dogs to do this and she was parasite free. Since the weather has warmed and we are back to our walking routine the rabbit chasing has stopped.
I don't know if this is a maturity thing but she does seem to have changed. She is more mellow than she used to be and also more protective. I think the new relationship was an adjustment for her. It just used to be "me and mommy and little sissy" and now there's this guy and another dog. He also has a cat and she's real interested in finding that and examing it up close. The cat, however, is NOT so interested. We have to really watch her around the cat. One minute she leaves it alone and the next she tries to chase it.
We'll just give this a little time, but not too much time if this is a health problem, and I'll keep everyone posted.