Question

friendship is based on faith and trust in princess's september

Answer 1

The fact that she realised how true her friendship with the bird was, was only when he came back as he promised her he would. It wasn't a true friendship when she locked him, thus severing the bird's freedom and not believing in him when he said he would come back. Also, the fact that she finally began to trust him and have faith in him shows how far they went along, because he stayed with her fit much longer after that.
(I'm not very clear on the details since it been a year since I did this)