"You can thank me by staying alive. That will be more than enough." Luna ignores the obvious - that given where they are both of them are likely to die sooner or later - and gets back to splashing water onto Sandy's wounds. A little more of this, and maybe she can move on to something else. "It's good that you've been learning skills like this. They're not always useful for helping yourself, but times like now..."

As much grief as Kyle gave her as a child (or as much care as he didn't) Luna is feeling glad she's actually had practice in caring for people if not burn treatment specifically. Knowledge alone is only so useful without ability. And that gives her another thought: "Actually, if you have a chance to help someone else with what you've learned, you can thank me that way. How about that?"