Alexa's expression when he talked about Norah being in hospital was clearly questioning, but she also realised it wasn't really her business anymore. Norah had been her sister, but that was a long time ago and Iain had cut that part of Alexa's life away. His siblings were his alone now, and Alexa was once again an only child just like she'd always been.
So she pushed the words back down, pushed the expression away, found what sarcastic comment she'd make if the conversation changed directions without her being ready for it.
When he offered her coffee Alexa thought something a little stronger would be a nice, but instead she said, "sure, why not?"