Geez, Matilda, I can see why you'd be uncomfortable. Could you go and "act as if" and let her see the incredible wife that your H has?
I think that if he invites you again, even if you've already eaten, you should go. That's just me--but I think it would make him feel good to know that you want to spend time with him and it would send a definite signal to this potential EA woman that she better back off.
