No offense, but I think communication and honesty will probably be more effective than spying on her ... which is what it sounds like you're asking. You might find a way to keep an eye on her without her knowing today, but when she finds out, it will only teach her not to trust you. She's a teenager, not a 5 year old, and that's when parents need to step up and learn to communicate with their children, rather than just trying to exert complete control over them.

Log on to www.kidsemail.org. The site has answers to your problem. With KidsEmail.org you can ensure your children are only receiving contact from approved people and that they are only sending approved information to others. One of the features on the site will enable all emails of your ward to be routed through you. The other features at kidsemail.org will enable you keep a complete check your child.