By default SketchUp has Auto-save enabled which will prompt the user to save the SKP file which will then also trigger the OS Plugin to open the Save OpenStudio Model dialog. To disable this behavior in SketchUp 2015, uncheck the Auto-save box from:

Window > Preferences > General

This will fix half your problem, but I don't think the user can disable the Save OpenStudio Model dialog without altering the code.can be disabled.