Find my iphone help, need to reverse it?

So i was on the app, find my iphone, and for some reason under my account it showed my sisters phone and where she's at. Now when i thought i was going to delete her phone from my account it restarted her whole phone. Can someone please help me reverse this?

Hold the home and power button for a few seconds until you see the apple sign come on the the phone will rest itself

I probably would go to the apple store close to me and find an answer
or get online and ask there at apple.