Larry, there are over the top dishes that would be good for vegans, that would make great Passover foods. I'm thinking stuffed squashes, eggplants, root veggies, such as honey glazed carrots, lentils/beans, deserts made with fruits and nuts, etc.
As you were invited, be gracious, even to you SIL. Eat well, enjoy your family. I found out that forgiving others cleanses us of burdensome feelings that can ruin what could be a pleasant get together with family, and friends. You are such a great guy. Let that show through in you actions. Be the example. Others will pick up on that. Though your SIL may be a pain, she is still the wife of your brother. I assume that you and your brother get along well. Maybe bring some kind of game that everyone can play, and enjoy, after the meal.
I am a firm believer in the power of forgiving others, and trying to set a good example. I have seen it change lives for the better.
My own wife was never much liked by my mother, father, or siblings, for reasons that are now obvious to me. However, they all loved me. My stepfather set the example on this one, and counseled my mother, and siblings to give my wife a chance. He told them that I loved her, and so there must be qualities in her to love.
Did I mention that my stepfather has always been one of my heroes? His integrity, honesty, work ethic, and the fact that he championed others against bullies, and ill willed people made him the example that I try to emulate.
Larry, be like my stepfather. You just might be someone's hero.
Seeeeya; Chief Longwind of the North
