MIL who lives in another state sent me this screen cap several hours ago - how bad is it?

Says she clicked on a Gmail shortcut, which I created on her desktop months ago only because she's prone to typing in or clicking on the wrong URL, she says that's all she did then BAM the mouse locked up, screen littered with over 20 popups, and a "Your computer is infected, call Microsoft Tech support at 855-337-6815" recording started running in loops.