Although present tense is used in Portuguese, in English we use the past tense here. "Since then, her behaviour has been excellent."
We can say "o comportamento dela tem sido excelente" (best option), or "o comportamento dela vem sendo excelente". (Portuguese present perfect does not mean the same as English present perfect)
The present perfect is being used in this sentence. (Used to describe an action that starts sometime in the past and continues to the present time.)
Past tense would be "was excellent".
you mean present perfect not past tense...but your example is correct
Also acceptable in English would be "deportment" (used for school behavior) and "comportment" (how one carries oneself in general).
Is desde really pronounced as deshy?
Where do they get "has been" ??
Where do they get "has been"??