Email already in use, but it's not

So I registered a user, but I made a goof. I mixed up her email with another person’s username, and since username can’t be changed, I deleted the account and went to add it again. However, WP is telling me the email is already in use. I search the userbase for the email in question, but nothing comes up. Do I have to remove the user from the database directly? How can I clear this email address from WP?

Thanks!