At the end of the film, Mother Nature congratulates all the Seven Dwarfelles for their contribution to Lord Maliss' defeat. Sunburn says that of course, some of them were better than others. Muddy scolds Sunburn for taking all the credit...nope, actually Sunburn meant Thunderella, whose lightning bolt came at an opportune moment to distract Maliss so Snow White could turn him to stone with his own cloak; Snow White would have been petrified herself otherwise. Then the rest of the Dwarfelles all cheer on Thunderella, who had been a klutz for most of the film.
Even before this; during the wolf attack, what does Sunburn do when they come closer while growling? She shouts Thunderella's name.
Even though he doesn't appear much in the movie The Princes determination to protect Snow White and help her and the Dwarfelles on the quest as the cursed Shadow Man shows why she loves him so much.