I think Eyecre8 already suggested this, but check out your friend's system. This seems to be an important peice of the puzzle. So far it seems to be the only unchanged variable.

Your countermeasures, such as chaning ISPs, countries while obtaining a NEW laptop would thwart most hackers. You'd think someone with this "ability" or persistence would embark on larger endeavors than making you life hell. Not that you're not imprtant

Back to what I was saying... It seems like her machine is the only constant and could very well be the hub for your troubles.

Let us know about this.