Cortana, as a being created from a digitized human brain, is a very humanlike AI. Take her current expression: it's exactly the sort of grimace you'd expect a human to make after hearing about someone nearly being eaten by alien spiders.

"Never thought I'd be so glad I'm not allowed to get married."

She glances over at the coffee machine. Still percolating. She looks back at Donna and tries to suppress the mental image of her being consumed by a swarm of tiny, scuttling spiders.

"So you got rescued by an alien. What happened after that?"