Weird Dog

We're dogsitting for our friend, and Isabel (the visiting dog) is used to sleeping on the furniture, which is verboten in our house. Our dog Lucy isn't really a fan of Isabel, because Isabel takes over Lucy's position as top dog when she visits. Last night, Lucy woke me up to go outside at around midnight. Then at around 2, she woke me up again, but instead of leading me to the back door to go out, she just stood in the living room. It took me a minute to realize that Isabel was sleeping on the couch instead of on her dog bed on the floor. I told her to get off and went back to bed. Then, an hour later, Lucy did the same thing, and Isabel was again sleeping on the couch. Essentially, Lucy woke me up multiple times last night to tattle on Isabel. She's a weird dog. How does one stop a dog from tattling? I can't seem to stop my 5-year-old from tattling, so what chance do I have with a dog who (presumably) has no language?