What iOS do you mean by new iOS? iOS 6.3.1 is the newest public release.
If your friend has jumped the gun and installed iOS 7, then all I can recommend is to go back to iOS 6.1.3 until iOS 7 is released to the public.
Either way, Safari should not have disappeared unless it was turned off in Restrictions. Do a search for it on the Search page. If it's been hidden in a folder, the folder will be listed to the right of Safari in the results.
You can also try telling Siri to Open Safari. If the app is present and not restricted, it will open.
One last thought. If your friend has jailbroken, check all the tweaks.
Good luck.