Hope is the only character that has no basis in the original film. She's a wishing star, and the mother of our main star boy! Her name comes from the first wish she ever granted for someone. They simply wished to have hope. Along with all the other stars in Rosas, she was pulled out of the sky and locked up in the castle by King Magnifico, forced to stay concealed and grant wishes for the King so he can take the credit and keep up his image to the people of Rosas.
Hope is very motherly and kind, but not in a condescending way like Queen Amaya. She's much more loving and caring despite not being able to be in her son's life, a foil to Queen Amaya who raised her daughter from infancy and still abides by her own conditional love. If it helps to get an idea of what Hope is like, she's meant to be modeled after the Blue Fairy from "Pinocchio".
Her voice is meant to be ethereal and kind, like an angel or (fittingly) a fairy godmother. Singing voice is a bonus, but it's not required(feel free to sing the first couple lines of "A Wish Worth Making" if you feel comfortable in that regard).