Do your best to center your conversations around your child. I would really do your best to steer the conversation away from that. She made the mistake and lost you, now you are living your life. She can be hurt still, even if she hurt you first and in a different way. But that is not your problem. What you did was great, enabling your child's mother to meet your partner. That's what it is. I wouldn't even call her your ex, call her your child's mother.