How Do I Change a Default Email Address?

When there is a blank space in a few different browsers in which an e-mail address is required, I get a pop-up to auto-fill with an email address that is not mine, instead of showing my email, it shows my wife’s email address. She does not have access to my computer, and the only place her email would be listed is in my address book or when receiving an email from her.
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Mike Anderson