i hate this aspect of her personality. You shared 3 years of your life with him. You're unable to have any relationship with him whatsover because you broke up? You can't congratulate him or feel happy for him? So his only value to her is as a boyfriend? If he's not that it seems like he's worth very little to her.
She acts as if they have to be strangers when it's not true. She's being an asshole to him for no reason. And I get her wanting to move on, but she already did. Not cool.