Promiscuius Girl causing trouble in friend's marriage.?

There is this girl (who is still in high school, 15) who is really creating trouble with people and thier "significant others", especially this couple who just got married. My friend, "Jane" got pregnant last year and the two got married. (She is 19, and he has graduated.) However, there is this girl, "renne" that has been bugging them for THREE years, and is obviously obsessed. My friend has tried eveything to get her to back off, and I mean EVERYTHING. "Renne" shows naked pictures to my friend's husband on his cell phone and sends sexual texts to him. My friend tried calling the network and they cannot block the number. "Renne" has also tried to come onto my boyfriend as well. Lucky for me, he was able to push her off. Plus we don't live near them anymore. But She has done this to a number of people at school, and we don't know how to make her stop. (We have tried talking to her parents, and they don't believe a word of it. And, unfortunatly, my friend deleted the proof.) PLEASE HELP