May you have some chat logs with her? Try searching your chat logs folders fully with the part of the email, it may show you some results.
Also, may she still have you in her contact list? You may have a look at the "Display who have added you to their lists" in Tools>Options>Privacy> (Before searhing this list, you had better show your contacts with their email addresses from "Contacts>Display contacts>Email address" in the Contact List window's menu.)
Also here you can have a look at your Allow and Block lists too. She may still be sitting in those lists.
Also, I don't give much possibility but, try searching Windows Live Spaces with her name and surname if you can recall.
http://home.services.spaces.live.com 
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