Tell her that we're god damn experts at computers. A good portion of this community has been using the computer since the late 90s. An even greater portion are building their own desktops.
We know what we're talking about when we say "McAfee is a whoring piece of stuff and MSE is just as good", even though most of us don't need antivirus software because we're not morons.
Otherwise, go into the settings and disable any automatic scanning or background scanning.