How to stop my boyfriend's ex from harassing me?

[Common Sense]

You are right, he needs to ignore her completely, like you are.

I would copy all of the evidence and take it to the police, WITH your boyfriend by your side. They will most likely make a courtesy call for you by asking her to stop this nonsense or she will be charged with harassment or what have you.

You and your boyfriend have to be much like parents who stand united to discipline a child (his ex), by always following the same rules you two agree upon. In this case, ignoring her. You see, by him contacting her, she gets her way as she has manipulated him into getting what she wants: his attention. Even if it is negative attention, in her mind, getting ANY attention is better than no attention at all. Let your boyfriend read this so he understands he is making a huge mistake and is actually rewarding her with his attention for her bad behavior towards you.

So, she has no motive to leave you alone because her contact with you, causes him to contact her. You see?

STOP ALL CONTACT. Period. NONE.

Once she is not able to manipulate you both, she will not get a payoff of the attention she craves and she will eventually leave you both alone.

If your boyfriend does not cooperate with this solution, then he is also getting something out of this and therefore, he is not being authentic and needs to be dumped by you.