Here's a theory for you:
If Tira hadn't been raised in the Bird of Passage, she would have been a totally different person. Can you imagine this young girl being protective of the human life, instead of being obsessed with killing others? Can you imagine her being Sophitia's best friend, being friend with Cassandra too? Being the Godmother of Pyrrha, instead of her tormentor?
I sure can, but that's just me.
But keep an open mind and try to think:
Tira was raised in her familly, who travels with a group of wandering entertainers, kinda like a circus. She retains certain caracteristics we already know about: she loves animals, hate keeping them in cages and help caring about them; she is gifted with gymnatics and dance and she learned to defend herself thanks to the teachings of her mother. She lived a happy life, full of love and respect.
Then one day, when the circus stops in Athens, where Sophitia lives. That is when the evil seed rains from the skies... Every one in the group is infect of dies, except for Tira who is rescued by Sophitia...
I know that this theory is farfetched, but just imagine if she didnt live the life we know she had? What if she was sided with the good guys?
what do you think?