"She is a sweet girl."
Tłumaczenie:Ona jest słodką dziewczyną.
It's true that a puppy can be "cute" or "sweet", with almost no difference in meaning.
But while cuteness is more about appearance, or sometimes behaviour, (and usually reserved for puppies, babies and young girls), sweetness is often about character. We rarely say that somebody "has a cute nature", for example, or talk about our "cute old grandmother".
And if someone does something nice for someone else, they may say "That's really sweet of you", but they'd never say "That's really cute of you"
So I think it would be wrong for learners to think they were synonymous.