Vivacious is a synonym of light-hearted.
As adjectives the difference between vivacious and light-hearted
is that vivacious
is lively and animated; full of life and energy while light-hearted
Lively and animated; full of life and energy.
(rare) Difficult to kill.
* (lively and animated) animated, bubbly, ebullient, high-spirited, lively, vibrant, exciting