I agree it's definetely a violation. She shouldn't have done that it was wrong. I would probably be mad too, but in a way, this will teach you to limit what you say to some people. But she is your sister and she does care about you and probably just made a mistake. Don't let her get in the way of your wonderful news and wonderful new adventure coming up
CONGRATULATIONS! Maybe you can talk to her and ask her why she did it and tell her the truth, that you don't appreciate it and it's a violation of your privacy. Ask her how she would feel if you went through all of her emails.