What version of Windows are they using?
Are they running under Virtualization like Parallels?
Assuming they are running Windows 10 “Creator’s Edition” (1703), then:
In Rhino Options > Toolbars > Size and Styles, set Button size to Medium and Tab size to small.
Rhino 64-bit desktop shortcut right-click > Properties > Compatibility > Uncheck “Override high DPI scaling behavior…”
Windows display - Right click on desktop > Display settings > Scale and layout > use recommended size (mine is 200%), and Resolution use a recommended size.
If they still have display problems, have them run the new “SetDpiAwareness” command and disable it, and restart Rhino
Does that get them sorted?