Lord Mark decides to pay a visit to Susan and Milly, and he seems intent on getting Milly to believe that he's more interesting than she thinks. He invites them over to Lancaster Gate and the group hangs out some more, talking now and then about how lovely Kate Croy is.
Aunt Maud invites—nay, commands—Milly and Susan to come stay at Lancaster Gate and remain there. She tells them they can stay in any room they like. She's really overbearing about it, though, saying that Milly must let her (Aunt Maud) be her caretaker and decision-maker. You can already see how Aunt Maud thinks of Milly as a possession she wants to take from Susan.
Aunt Maud has a nice candid moment in which she says she's so happy to have made a new friend. She says at her age, she can't make friends out of the blue, which is why it's nice she met Milly through Susan.
Milly feels comforted by Maud's protective personality. At the same time though, she realizes that the woman is pretty much an unstoppable force when it comes to making plans for others.