Grub and Windows update

[Bill]

Hi,

I am installing Linux for a friend that has a nasty Windows virus.  
Rather than pay mucho dollars to have the virus cleaned from her 
computer, she decided to migrate to Linux instead.  (Good idea!)

The issue is that she wants to dual boot her computer and use Windows 
for only playing games (not online) and use Linux for everything else.  
The problem is Windows update.  Since Grub will replace the Windows boot 
loader, can Windows update affect the Grub boot loader in any way.  I 
have dual booted my computers with no problems ( I have no experience 
with Windows 10)  but hers is Windows 10 and I heard that Windows update 
can be more intrusive affecting even the BIOS.  How could I disable the 
network (in Windows only, not Linux) so there is no internet access when 
she is using Windows?

Another possible issue is UEFI.  Should I disable UEFI in the BIOS?

Bill Stanley