Morella is a very friendly and welcoming student, and is Lenore's roommate. 

Morella proves to be an incredibly kind and approachable person, who is very eager to start friendships with the other students of Nevermore. She is slightly dense, but it adds to her charm. She is shown to be very caring, especially for her loved ones. She's also shown to cry easily and is very emotional.

When she was alive, she was apparently very heroic and selfless, as she died trying to protect someone else. This also came with her to the afterlife as she refused to leave Lenore behind in the Teraphobia trial, and ended up saving her from death.

I see her voice as high-pitched, with a large range of emotions. One could even try to give her an Irish accent!