Talitha is upbeat, a bit dense, and very childlike. She sounds on the younger side, but her voice can't be extremely obnoxious or high-pitched.  She will say some words that are in her native language, which is a non-Existing language called Rorrim.

The voice I always imagine is something like Meredy from Tales of Eternia.  But since she's never been voiced, feel free to try your own take on what you think the character could sound like.