You offer Moondancer to buy the item for her.

Moondancer: "What? No, that's—"

Moonflower: "Ooh, let's do that! She helped us with the treasure, so we should let her have some of the bits we found!"

Moondancer: "I don't—"

You trade 25 Gold Bits for Phoenix Quill Pen, which you give to Moondancer.

Moondancer: "Wow, I... I don't know what to say. You really didn't have to. I mean... thank you so much."

You tell Moondancer that you're more than happy to help.

Moonflower: "Yuh uh!"

After thanking the shopkeeper, you exit the antique shop.

Moondancer: "I just know she's going to love this. I'll head back to the inn, and gift-wrap it right away. See you at dinner."

You bid farewell to Moondancer, and she happily trots off to the inn.