It's an unfortunate part of being online, viruses.
This is probably a good chance for everyone to have a wee check of their computer security.
Make sure your virus software is a good one, and up to date. Make sure that you regularly update your browser (internet explorer, chrome, firefox, whatever it is you use). They often send out security patches but you must do the updates to get them. If you recieve an email with an attachment, even if it promises to be the funniest email you've ever seen, don't open it until you've checked where it came from. Remember if your friend gets a virus, it will take control of her computer and send itself out to everyone in her address book. Which means you won't get a virus from looking at dodgy sites or ordering "pleasure enhancers" from Thailand, you will get it from a friend. :-)
Don't be afraid to delete emails before opening them if you're at all suspicious. The world won't end, your friend won't stop talking to you, and it's highly unlikely the secrets to world peace or the cure for cancer will be contained therein. ;)