"She is quite good."
Translation:Ona jest dość dobra.
Commonly, you could say that, but in this case I wouldn't recommend it unless the English sentence would be "She is rather good".
There is a subtle difference between "rather" vs. "quite" and "raczej" vs. "dość". If you would rank something based on quality, you would put something that's "quite good" higher on the list than something that's just "rather good".