Bought an iphone from a girl who reported it stolen, what can I do to start using it?

So I recently bought an Iphone for Verizon from some girl. A couple of days later I went to Verizon to try and activate it, but wasn't able because it had been reported lost/stolen. I KNOW it was that girl's because the day I got it I was still receiving text messages addressed to her, but unfortunately I deleted them like a dork. So what I think she did is report it stolen in order to get a brand spanking new phone with the phone's insurance. I called customer service and they said if she could call in and say she found the found they would take the phone off the list no questions asked and I would be able to use it. The only thing I could think to do was give the girl a letter saying if she did not dismiss the report I would take her to court with the text messages and evidence as proof (but I obviously deleted them so I was just trying to scare her into it). I gave her a one week deadline, she has one more day and I doubt she will dismiss the report. My question is what can I do to start using this damn phone or who do I report this idiot to? Sorry this is so long

You could try replacing the card in the back with one from another phone. Then delete the info. But that's a guess, no promises.

There's really nothing you can do activate it until she reports it as not stolen. I would confront her about it because she's scammed you pretty bad. Phones cost a lot of money retail wise and if she says it's been stolen and that you stole it, you could be in a bit of trouble.
If she won't respond to your letter, you need to take some sort of legal action. She sold you a phone and it can't be activated. Either she stole it and sold it to you, or she did as you said and was pretty slick about it.

Oh, and about the other answer, Verizon hasn't used Sim cards in their smartphones until quite recently with the 4G LTE phones.
And the IMEI would be flagged as 'stolen' and wouldn't be able to be activated. The IMEI is like the phone's fingerprint.

Just jailbreak it and unlock it! Then you will be able to use it again! Just do a google search for your phone type and the iOS.

Report it to the police or here insurance company if you know it. Plus if you receive the txt from her you could probably still get the record from your service provider. Service providers need a reason to disclose this information and required your consent so you could report it to the police as fraud and get them to get the evidence from your service provider.