Well. This is new. Whose dream is this Bianca's wandered into?

She sets that aside. This is too delicious an opportunity to waste wondering about the anomalous Dr Brennan; so she smiles at them both and answers them both with an air of sympathetic understanding.

"What else would a mother do? And he is worthy of your faith."

Bianca finds, somewhat to her surprise, that she's speaking the truth. She may find Mello hilariously immature in some ways, but she enjoys him. He's a worthy opponent, and that is almost better than a friend.