i'm really glad your dad knows about this.

if you have her first and last name then you can do a people search and hopefully find out her home phone number. i really think her parents would want to know what she's up to but your dad would be the one to talk to them. i know it would be awkward but you need her out of your life and she sounds like she needs help because she's really out of control with how she's been after you.

another option is if you have your dad talk to someone who is knowledgeable about internet security they might be able to block her from your computer. i wouldn't have your friend talk to her. it would be better to cut off any communication to her altogether so she'll eventually move on. more communication, even thru someone else, will just encourage her to continue. she sounds sick and needs help. there is no sense to her behavior so trying to make it make sense probably won't work.