How to get rid of a crazy ex-girlfriend?

I'm 19 years old and my boyfriend of 5 months is 21. Everything between us couldn't possibly be better except for the fact that he has a crazy ex. Without giving too much detail, I saw their relationship through it's entirety. It wasn't pretty, actually borderline emotionally abusive. She chested on him numerous rimes, even hiving him STDs. They dated on and off for about two and a half years, they had been broken up a year before he and I had started talking. Within that year she had shown up at his house, stalked him at work, everything imaginable. Well, he has blocked her calls, texts, and on Facebook. The only contact she has with Jim is through email, which he had forwarded to another account which for some reason messes up the block. He doesn't respond to the messages, but gets several a day. She also still shows up at his work, where he will go on break to avoid her. They've had several "break up" talks, yet she still persists, she has even told me that they've been sleeping together, which I highly doubt. My question is what can I do? He has done everything in his power to ignore her, but it still causes awkwardness and tension in our relationship. Help?