Hermione reacted rather quickly to the bright flash of light, casting a quick "Protego!", a shielding spell, so that if there was an explosion both Reynard and herself would be protected. (There have been many young wizards who had caused a fire, when they were learning the Lumo spell).

She places her free hand around his waist too, just in case she needs to shield him.

But the spell ended in a completely different scenario. Hermione looks around to the flawless coat of snow, and laughs softly herself. Her arm that had been at his waist, gently touches his back, when he doubles over in laughter.

"That was expected!"