Boyfriend visits online dating sites dating spoilt woman
Each one of us felt lonely at least once in their lives.
Just knowing her email address will not allow you to find out if she is on a dating website.
I know that this must be a difficult frustrating situation for you but if there was some other way besides asking her or seeing her computer screen I would tell you about them.
I understand you may not like this answer but it is 100% accurate and the truth.
Since she is using devices that you do not have access to then there is no way externally that you can tell what she does online.
You did mentioned you searched for her name however this will not really work unless she joined a website and used her real first and last name.