All the options (velim, velis, velit) are possible. “I, a girl, would like a pastry”; "You, a girl, would like a pastry"; "She, a girl, would like a pastry” ( = "The girl would like a pastry”).

Again, classical Latin does not use the subjunctive in this way. Vult should be the correct verb here. Independent uses of the subjunctive do not show politeness.