[It is perfectly understandable, and the troubled hint to Merlin's expression goes away completely as he grins wide and just looks at Charlie. He knows, in the very moment she wipes at her eyes, that he made the right choice to go through with this - which is confirmed further when she hugs him.

Idiotic, he's sure plenty would say, but he won't regret it.

He puts his arms around her in return, tight, and presses his lips to her hair as he chuckles.]

You're welcome.