I don’t think we can tell you what to do.. haha. But I’d see it this way. You married your husband. He chose you over the ex gf. Be proud of it. Maybe he wants to go and really wish her well because she also found the right person to marry. Maybe he wants to show you off. Either way, if you do go, dress up beautifully, feel confident and enjoy the food! 😁
I think it's fine to go but of course go with your gut feeling...No one can force you but if you do go remember to smile and enjoy the evening!