Update
Thanks again for all the help. Virgin Mobile would not insure or guarantee a certified preowned 4s for more than 14 days, so could not find a 4s that will work. Just don't see spending $400 on a phone for a teen, maybe when she has a job.
So we bought the 4 at Radio Shack at 5 am for $99. Should keep her happy for a little while and we can monitor how she takes care of it. By next Xmas, we'll look at a new one!!
For now, I am less stressed. She is happy and wants Uggs to go with her iphone since we got such a bargain price! Sigh...14.