V2V is Virtual to Virtual
According to info in the support bundle the two VM are currently only sin less then 10 GB Host disk space when not running. When running an addition amount of space it temporarily used by the .vmem file for each VM in the size of the RAM allocated for each. This is then released when shutdown, not suspended.
If all you have in the VM are the base install of the OS then it just may be easier and faster to delete the existing virtual hard disk and then add the size you want then reinstall the OS.
BTW If you make the proper choices as you walk through the New Virtual Machine Assistant you can take the opportunity to modify the virtual hardware before installing the OS.