I am using split screen sofware of LG but it is not working for me with vmware fusion 7. Split screen software of LG ultra wide monitor won't start with windows 7 installed with VMWare Fusion If you don't get help here, you may want to contact Fusion's tech support. This sounds like it could be a Fusion issue. My screen does extend but I am unable to interact with anything on the second monitor.
In VMWare I am unable to use the secondary display effectively. I am using a Mini Displayport to VGA adapter which works fine in except when I use it with VMWare fusion. Mini displayport to vga limits second screen resolution in VMWare Fusion