Here is from the docs:http://www.vmware.com/pdf/horizon-view/horizon-view-client-mac-document.pdf
Monitors and Screen Resolution
With View Client 2.0 and later, if you use the PCoIP display protocol, you can extend a View desktop to multiple monitors. If you have a Mac with Retina Display, you can see the View desktop in full resolution.
Using Multiple Monitors
If you use the PCoIP display protocol when accessing a View desktop, you can use up to 2 monitors, with a resolution of up to 2560x1600 per display. If you are using 2 monitors, the monitors can be side by side or
vertically stacked.
When the 3D rendering feature is enabled, the maximum resolution is 1920x1200. Examples of 3D applications include Windows Aero themes, Microsoft Office 2010, and Google Earth.
To extend a View desktop to multiple monitors you can use the Window > Full Screen menu item or the expander arrows in the upper-right corner of the View Client window.
If you have a Mac with OS X Mavericks (10.9), open System Preferences, click Mission Control, and deselect
Displays have separate Spaces to use full screen with more than one monitor. You must log out to make your changes take effect.
Make sure that he/she is using the latest client, 2.3.
// Linjo