Mirroring Database tables and views on SQL Server Express
This is not a question of replication, nor mirroring. Is about updating the app.

You should have a deployment strategy for your app, including upgrade. Updating the 'demo' would simply mean running the normal deployment of you app. Read Version Control and your Database. Study Rails Migrations, they're a great example of deployment control. Read about EF Code First. Stop updating the DB directly. think in term of source files.