Maximum Ride Theories
That Angel has a voice like Max's. This is hinted in the 6th one.
Also there are many instances in the books in which angel knows thing that her mindreading cannot cover.
For example.
-Angel knowing the password to the "Max Card"
-Angel knowing fang was going to die.
Angel might also have a voice because she is "supposed" to lead her own flock. Max is a leader and she has a voice, Angel is to become a leader (according to the books) so she gets a voice.
This Theory is by I'm short.
Thankyou
And for anybody reading this if you do have any theories of your own feel free to send them in.
Ruby