My name shows up on my wife’s outgoing emails.

This problem started yesterday out of the blue. Everything was fine until then. I have a one month old laptop with Windows 8.1 and Windows mail. I have a Microsoft account. My name shows up on the signon screen. I have 2 email accounts set up on this machine, one for me (call me Marty), one for my wife (call her Debby), using 2 different email addresses as always. Up until now, outsiders saw the name Debby on her outgoing emails, and Marty on mine. No problem. Now her outgoing emails say Marty. Funny though, her emails to me still say Debby. I have gone into the "PEOPLE" contact list but only see the correct names for both of us. I do not see any Marty associated with her email address. However if I sign on to her email and create a new message and start typing Debby, it lists 2 Debbys, one with my email address, one with hers. I can't find where the one with my name on it is located. Is her email's name defaulting to my account name?

btw I am still getting used to Windows 8's weird quirks but overall I really like it.