Steven is visibly shaking, and pulls back his hands to cover himself the moment they are let go by the force inside his prism. He doesn't get what she means. Diamond?

The first thing that comes to mind is that the Blue Rose somehow changed him. But yet... The Blue Rose wasn't any particular gem. It was just crystal growth, something else completely. It makes his stomach turn a little bit regardless. He doesn't know what that means, but it's forboding.

"I'm... I'm sorry," is all he manages to say. Is it sincere? At the moment, definitely yes.