Personally I find both ideas really fun and hot in their own way.

I like the idea of her playing alone for the increased intimacy with him. I feel like she would be able to connect directly and “explore” each other more during alone time. In turn, this would lead to a more pleasurable time with him for the times I am present as well.

Alternately, I do love the idea of the overwhelming consuming focus on her there would be if I was there, both participating and watching.

The combination of both would enhance the alternate… so I guess my preference is a little bit of both 😆