Surely they're all on equal footing here. (With some more equal than others, of course.)

"Just a little tickle. Nothing to fret about. Winter, draughty old castles. What we both need is a nice warm drink and a seat by the fireside." Her smile is still a shade sickly, but there is a genuine interest in her tone. She might not approve of Grainne, but she wants to hear what she has to say.