I have a fussy eater with food aversions so I always take food for her but my other kids would love that food and we eat similiar food at home - I am a very keen home cook and love to entertain!
Eta - and does that describe your SIL? Not so much "very competitive" but a keen home cook who just loves to cook good food?
And eta again - if we have families with children coming and I don't know their tastes very well, I do make sure there are plenty of things like little dinner rolls, tasting type plates with little bits and pieces etc so that at least there might be something they can try, but I don't do nuggets, or sausages etc just because there are kids coming. I don't eat processed nuggets or processed sausages and the like and I certainly don't expect children to either iykwim?