It's a defense reaction. Certain individuals in the comic industry have attempted many times to erase that part of her character.
How is it a defense reaction?
If anything it has more to do with with it not being relevant to most of the stories she is in and that constantly pointing out that she's a jew takes away from a core point of the story, the distinction between humans and mutants.
Mutants in the story are talked about as a separate species; despite the fact that they fail that classification in almost every way since they can still interbreed with normal humans and don't have any mutually shared collective traits, but that's just my autism talking.
The point is "humans vs mutants", even Magneto's entire backstory with being a jew during the time of the holocaust is used to justify the distinction between humans and mutants rather than humans and jews. The holocaust narrative is just a setup for Magneto to be a genocidal race supremacist in the same way Hitler is portrayed in comics. Once Magneto goes full mutant Hitler his jewish origins become a footnote in his story.
With Kitty her being jewish is a footnote in her story, the star of david she wears is more of teenage girls fashion accessory than a meaningful part of her character and so a lot of writers just gloss over it. Not only that but her most liked designs have her portrayed as a ditzy upper middle class White girl rather than a jew so those elements are carried forward more often.
It's like people claiming that writers are trying to erase Superman's bible belt upbringing origins, it's just not a relevant part of his story.