A shy and sweet Keyblade wielder chosen by Ava for a special task. 

Strelitzia is a quiet and shy girl who is considerate and caring for others when she realizes that those who are not Dandelions will perish in the war. When chosen to be a Union leader, Strelitzia expresses doubts that she is qualified for the role, showing lack of confidence in herself.

Since she doesn't have a voice actress in previous games, I can imagine a soft-spoken, polite, and high pitched tone for this character. You can also try to do whatever voice seems fit.

(Fair warning: This character is crucial with emotional scenes so be prepared with this role!)