As someone who has been in your exact situation, you do not come between your husband and his relationship with his mom. If he wants her there, then you invite her, you be gracious and civil, however you do not have to speak with her and be all chummy with her. Besides there will be plenty of people for you to socialize with, don't let her ruin your day. And one more word of advice, make sure to discuss this with your husband. If your husband isn't prepared to stand up to her and defend you if she says something bad about you, then you may want to rethink things otherwise it will be years of battling with both of them. I'm lucky enough to have a husband that supports me and stands up to his mom, it has not affected his relationship with her but she knows not to say or do anything to me in his presence!