All my e-mail addresses and some of my e-mails are appearing on someone else’s system. How can I correct this error?

About a year ago, I helped a friend set up a Hotmail e-mail account from my computer. Since then, all my e-mail addresses have appeared on her people listings, and many of my e-mails, especially related to social networking accounts have appeared in her inbox. I don't understand how my e-mail account has become linked to hers. I don't know how to resolve this error.