Amy is the protagonist of the game, and she's the only one who's not an Ultimate. She is an introvert and is better at listening than talking. She loves reading and spends most of her free time devouring books. She's really curious but gets startled easily. She can be a little sarcastic and pessimistic at times.

As for her voice, I'd say it's low and soft-spoken. If you need a better example of what I have in mind, a reference I'd give is Aimee Mann in the role of Opal in Steven Universe. Here's a link to some of Opal's lines: 

https://youtu.be/qy40KdLDK7s