A google search shows some options. Personally I've always found anti virus Mac software to cause lots of issues and to be way more trouble than they are worth.
I noticed that the latest version of Flash puts up lots of annoying alerts for no real reason at all. Really wish Flash would just finish dying and go away.
JAVA is all but dead and disabled by default.
If she is running Mountain Lion then it has Gate Keeper built-in. Even older Mac OSs have a form of Gate Keeper but with no front end interface.
I'm running Snow Leopard. I don't worry about viruses but since I do download a lot of software to try out I have some concern about trojans I run
Little Snitch so that I'll know if something is opening up a port and sending information without my permission.