internet- ugh!!

Hi! I am mom of a 14 girl. She has gotten into trouble with the internet and cellphone in previous foster home and continues to do here. She will be in our home for almost a year now. Last fall she posted a message on facebook insulting old people, talking about penis and giving out our home number telling people to call her if they agree with this message. We had a very lengthy talk. She was grounded from internet for a month and she had to sign an internet safety contract to get back on. We also told her if she broke the rules, punishement would double. Within a week, she broke the rules. She created another fake facebook page and had some sexual verbage and she was sneaking on internet through DSI past hours. So we told her she was grounded off for two months. During this time, I found a note giving her boyfriend a new email address and password. She was sneaking on the internet at school. With this new email acct, a friend of hers sent pics of her boyfriend and his private parts. I created an acct of my own and posed as a 17 yr old boy. The talks we had with her about internet safety obviously did not sink in at all. As she did not even know how this 17 yo (me) was and linked him as a friend on yahoo "to stay connected". I gave little info about this 17 yo (me) and by the third email, she sent a message back giving out our home number and if her parents asked, he was a friend from Mpls. I/17 yo boy did not even have to ask for her number!! I guess I shouldn't be so appalled but I am. My husband and I are at a loss of how to handle this. What is our next step and how do we get through to her about being safe? We have not confronted her and she does not know I was this 17 yo boy yet. Any advice?