She takes the bottle with the hand above which scar is, making the decision to let him see. He's been forced to show his back scar to them by Raphael, which was a terrible and offensive thing for the demon to have done; all of his trauma laid bare so suddenly that Hermione hadn't even been able to say she knew what that felt like.

She is going to take a wild guess here that he doesn't want to talk about it, so she shows her weak underbelly first. Metaphorically.

"I have a vague idea of how they can be."

She has some goblets somewhere, grabbed from an old dungeon for the road because We're not barbarians and pours some for both.

She takes a long sip and lets out a sigh. "Alright - now can I be sentimental? I'm not used to people noticing when I'm injured, and I know you'll want to brush it off as some mention about how bad my blood smelled or something but I'm still very grateful."