Because she won't just take them into her bedroom and play?
They either end up just randomly standing downstairs whilst I'm trying to get on with things, OR doing something that is annoying and/or takes over the whole house, for example going from room to room opening and shutting doors constantly and playing in mine and DH's room, or constantly going in and out of the front door and leaving it open, so the dogs escape etc.
Last week she brought in 2 neighbours' children to play and they all kept forgetting things they'd left downstairs and charging up and down the stairs. They must have all gone up and down the staircase 50 times....
When I was a child if I had a friend over I was expected to play with them in my room. I certainly never took over the whole house with a game or just stood in the kitchen for 2 hours with a friend.
DD is 10 btw