Nao is initially timid and shy and primarily stays with her teacher Professor Mishima, whom she idolizes to the extent of wanting to stand in anyone's way if they say negative things about him.

However, throughout the game, she gains immense mental strength and displays that she is no longer easily manipulated.

To go more in-depth on her voice:

Nao is hard to put into words. Yes, she is a sweet and kind person, but that’s not the 'be-all end-all'. I would say that she’s easily flustered; and not necessarily in a ‘romantic’ way. For example; when she says “There’s nothing guilty about us!” she’s flustered/awkward, and in her haste to prove her trustworthiness, she says something that actually makes her seem more suspicious. What I need for Nao’s voice is earnestness. She can be awkward and can say things she doesn’t mean to say in her panic, but something about it is endearing. And when she’s talking about something she’s passionate about, she really shines. Her earnestness is so genuine that any doubts you may have fade away. Plus, she’s also very expressive. Don’t tone down any of her reactions. She’s not on, say, Ibuki’s (SDR2) level, but she comes pretty close.

And ofc she genuinely admires, respects, and even loves (NOT romo) her Professor. It’s very likely that she decided to be an artist because of his class (or, more precisely, that she obtains the confidence to do so from him).

//spoilers?// his death is absolutely devastating to her. Her actions after that scene are completely understandable; she's just lost one of the most important people in her life. 

And finally, on a more pleasant note, she’s definitely wlw.