Report it as stolen.

no she stole it, you can call the police om her

And this is what the police are for. You get your phone back, she gets a court date.

"Finders keepers, losers weepers, yet theft is still a crime. Enjoy your court date."

I really hope that you went to the police.

And why didn't you do that about an hour after it went missing?

So you call the police. You report it stolen, along with "yes I know who took it, here is her address."

Is your sister in law 5 years old?

I’d smack a bitch lmaoooo

Use Find My iPhone to lock the iPhone so she can’t use it.