I allot 30 minutes to an hour for a M&G, depending on the situation. If the client is new and I am boarding the dog, I allot 45 minutes. I play with the dog a little to get them used to me, let the owner & dog explore the house and the yard, and give the dog some water, with owner approval. I then sit down with the owner and go through my checklist of questions. I explain my usual daily routine and confirm the dates of the stay, including dropoff and pickup times, with any day care fees if appropriate. I then ask if they have any questions. At that point I stand up and tell them I would love to keep their dog and that they have 72 hours to book and pay for the stay.
If I am visiting the dog, I also allot 30-45 minutes. I meet the owners and dog(s) and pet the dogs. I have another checklist that I go through, emphasizing that I want to replicate their normal routine. I make sure I know where the food and treats are kept, what times they are fed, if the dogs are to be walked, and if there is an alarm system. I explain what I will do during my visits and ask where they would like me to put the mail or any packages.
I've never had anyone ask for a second meeting, but if they did, I would tell them they can call me with any questions they may have.
Normally around 30 minutes, maybe you can ask her politely why she needs a second meet and greet? She have already seen your house, you, your dog.... If she has any other question it can totally be solved through rover messages. Good luck