"Love is sweet" describes a person or actions of a person that are simultaneously sweet, endearing, and slightly cringe-worthy. Often attributed to those with an "old soul".
The person being described as "love is sweet" would likely feel embarrassment knowing what they did was observed.
You will always feel affection towards "love is sweet" people and actions.
"Love is sweet" cannot be fully understood until experienced.
Observer 1: She recorded herself dressed to period listening to 20's music!
Observer 2: love is sweet...
Person 1: *tries to sing when they know they shouldn't*
Person 2: that's so love is sweet!