Binoculars,
I'll tell her to say no to anything she's not sure about and reinforce the notion of never opening an email unless she knows who it's from.
That is the number one way people catch viruses, it is because they open an email from a known person/friend. Most viruses will go in on an infected computer and send itself via Email to everyone in the infected computer's Address Book and then it will go though every email ever sent or received from that computer and send it to all of them too.
You need to explain that she should not open any attachments even if it is from a friend unless you knew prior that it was coming!!!
Take care,
Richard