Hi there, I had the same situation, where I could not delete/drop the databases.

Here is my solution:

1. Alter database <Databasename> set partner FORCE_SERVICE_ALLOW_DATA_LOSS

Once you executed this command, you can check the status of the database by refreshing MSSQL Server Management Studio.

You can see that it now changed to (In Recovery)

2. Use MSSQL Server Management Studio, manually change the database properties.

. Right click on the database and go to its properties

. Go to Mirroring, then Click on Remove Mirroring

. Click OK

3. Refresh MSSQL Server Management Studio, then right click on the database to delete it.

Good luck, I hope that helps.