Traduko - Portugala-Japana - Amo-te muito minha princesa

hime-sama daisuki
hime-sama is a perhaps overly romantic way to address your girlfriend (assuming this is for a girlfriend and not a daughter), but the translations reflects that you are close enough to person to say something like this. A pause between hime-sama and daisuki, and an emphasis on daisuki, may add effect.