Honestly, I think she's better off not becoming your MIL's computer go-to person - otherwise your MIL will discover that it's easier to call your DD about every little thing than it is to fix it herself (or go without) and your DD will really start to feel used.
I completely agree.
My personal belief is that if someone wants to use an item, say a computer, then it's their responsibility to learn how it works, firewalls, antivirus software, all basic, knowledge instead of relying on friends or relatives to do things for them that they're perfectly capable of doing themselves if they'd read the instructions (sorry, this is very triggering for me due to my mother acting helpless). Obviously, if more serious problems occur, then by all means, ask computer savvy experts since that's what they're there for, but yeah, basically, don't allow your DD to become the go-to person because your MIL will become dependent on it and believe she can't do it herself. That's not a road you wanna go down!
(Sorry, I think I've eaten too much chocolate at once. I'm feeling a sugar buzz and it's coming out in my writing!)