As her name says, she's really sweet and kind. She's the most mature of the dronies, well, behind Sunny that is...
Since she has dragon feet, which have special paddings on them, she can't slip on slippery surfaces, not even on a bannana peel. Her feet give special balance powers, so she can't be heardhwhen she is walking by. Her long hair actually has powers of their own. It can be use to swing up to high surfaces and lift others up. It's actually easy to sneak in and hide up on the ceiling, which she can climb up to with her claws. Even someone as sweet as Sweetheart can be surprisingly sneaky.
Sweethear is light pink all over, but her legs are magenta since they're actually dragon legs her father. Her claws are painted hot pink. She has really long hair on both her mane and tail. It's a lighter pink and has peach pink streaks. She's more like the drony-version of Rapunzel.