"nachmachen" means to imitate, to copy someones behavior.
"sie hörten es nicht" is a conjuctive clause, it means they wouldn't hear it.
I would translate your whole sentence that way (shortened):
She is a woman who is able to imitate people to the point that well - you wish them they don't hear it, because it's so pretty exact and ironic and stuff.
Sorry, my English is a bit too limited for that sentence but I hope it gives you an impression.