Having seen how Liam has reacted to some seemingly random flighty woman, Danielle thinks he’s tractable and thus useful. If she bothered to have any interest in other people she’d realize he was talking to his sister who has had lots of practice.

For the record, Liam’s about as resistant to Tara’s scary people skills as Rowan is. He seems to be giving in quickly because he and Tara have had long conversations, and arguments,  over how things would go long before the party started.