@Felicia222 If the guest is currently in residence, you can contact her and let her know that she has brought an unauthorized pet -- use that wording because she will probably claim that the dog is a Service Animal or an ESA. An unauthorized pet is a pet that was brought without your knowledge and consent. You can ask for payment via the Resolution Center for the cleaning necessary after an unauthorized animal. You will be risking a bad review, so decide if this is worthwhile.
You say that the guest has rebooked for the month of April. Let her know that your long-term rental cleaning fee (NOT a pet cleaning fee) will now include a mid-rental cleaning at X dollars. Let her know that if she brings the pet again, a rug cleaning will also be necessary at the end of her visit. IMO, any host who offers their property for long-term rentals should require a mid-rental or extra cleanings, especially when animals are involved.
Obviously I am annoyed by the numerous persons who bring their animals into our properties without our knowledge and consent. I allow pets, but I have to know your animal is coming so that I can arrange the extra cleaning time needed for the fur everywhere, the feces and the laundry (because of how many of these animals sleep with their owners -- ugh).
For the future, put the fact that you do not allow pets in the FIRST paragraph of your listing description, not hidden in the Rules. On another platform, a host posted a picture of a menagerie of animals with the NO symbol photoshopped on top.