I found my ex girlfriend on social media and I'm gonna start harassing her.
Why would you do something so cruel as harassing her?
I need to keep my eye on her.
Sometimes it is difficult to deal with an ex but you should not harass them online or in person. It could get you in trouble if they find out it was you. She is free to do what she wants, regardless of if you approve or not.
It's not like I'm gonna get arrested just for harassing her.
You actually can get in legal trouble for harassing someone, even just online. It gives them justification to place a restraining order on you. Even if no charges are pressed against you, harassing her is just rude and makes you come off as obsessed.