Ashkenazim tend to be more strict while Spharadim are more laid back.
Both traditions are fine.
As time passes and more Spharadim marry Ashkenaizm (or Latinas work within Jewish families) and visa versa, people care less and less about these strict aspects and blend them into something like a hybrid.
Israel today represents that hybrid.
There, the Jews mix everything into a culinary delight and a less restrictive atmosphere even though the Orthodoxy rules that state in terms of general observance. East meets West and the end result is a more resilient people.
I still think that if the woman’s in-laws want to keep an 800 year old tradition, they’re entitled to do so. She has the entire rest of the year to eat beans. It sounds as if a day off to show a little deference to her husband’s family might do her some good.