On a stock iPhone, a virus is impossible (app sandboxing). That's different if her device was jailbroken.
Are restrictions enabled on the iPhone? You find this in Settings - General - Restrictions. Enter a passcode if necessary, and then make sure Safari is enabled. This should being back the browser. To be allowed to install apps, enable "Installing Apps". Also take a look at "Allowed Content".
If you haven't done so: restore her iPhone using iTunes. Backup her device before you do so. Try restoring from that backup afterwards. If that doesn't help, set it up as new (also using iTunes).