[He aims to have her as much at ease as possible. Because it's bad enough to be like this without others adding stress to it, so he's actually pretty pleased to see her smile and seem more calm than she was some minutes ago.]

Don't worry, I'll keep a close eye on you. If there's any sign of Miss Mouth going on a trip somewhere I'll let you know... And catch the sandwich if those little hands decide to go on a trip too.

[She didn't seem very capable of holding things in that first form. He'll eat his sandwich extra slowly, though, just in case anything fails and she ends without hers, so she can eat the rest of his once she has a mouth again.]