Why do all my emails i send to one person go to all her friends after she sent a return path this is her name?

this is really annoying me she changed her email addy and and now when i try to email her it comes back to me and all her friends get it and send nasty messages to me.how can i stop it plz help me.apparently she had a return path thingy and it went to my email box and i didn,t know it was still there and her name was in and i deleted it.why is all this happening?help me plz