Advise needed for lovebirds!!!!!!!!!!!!!?

ok i just got a lovebird from a bird rescue place and i want to know if it was a girl or a boy. since they found the bird they have no clue what my bird was which was a girl or a boy. we just call my lovebird a she because of the name that they the place gave the bird. the lovebirds name is sweet pea. im not sure how to tell if sweet pea is a girl or boy. you see the lovebird sings alot. is there anyway to tell if its a girl or a boy?? i also have finches and i know if they are a girl or boy byt the color of the beak. if it were canaries or atiels i know its gender by the singing. becuase a male bird sings to attract its mate right so please help me out here.