A conventional way of saying "she's a nice person" is הִיא אָדָם נֶחְמָד (hee ah-DAHM nekh-MAHD). Note that אדם is used to mean person and stays masculine even though we're talking about a woman.
Another way of saying it that taps into the person's nature more deeply, is היא אדם סִמְפָּתִי (hee ah-DAHM seem-PAH-tee). Literally, this translates as she is a sympathetic person. If you've studied literature, you may be familiar with sympathetic characters - those characters with whom the reader identifies with, feels warm and fuzzy about...
Interestingly enough, that's exactly what Ulpan La-Inyan does with the Hebrew language - our students feel warm and fuzzy inside when they study with us.