Can you Mirror an Microsoft SQL compact Edition database
You can copy the database file to the desktop and use a tool like SQL Compact Toolbox to query the data
Or you could place a copy of the file on the SQL Server disk drive, and acces it via some SQLCLR code (this will allow you to mix with SQL server data)
Or you can use some synchronization mechanism to transfer the data to SQL server (requires programming/configuration)

Mirroring is not an option at all