Hi Cira,
If Joseph account is available, ask him to remove his proxy settings.
If his account is already inactive, make it activate and reset password, and administrator login ppm with his account and remove Joseph's proxy setting. After that, make his account deactivate again.
You are able to see proxy data in CMN_SEC_USERS table. Try to check Mary's data in CMN_SEC_USERS table.
You will find following columns and data.
PROXY_USER_ID (Joseph's resource id)
START_DATE (Proxy start date)
END_DATE (Proxy end date)
I don't recommend to overwrite above columns with NULL value because it maybe cause any side effect.
Regards,
Shoichi