Well it is political yes. And she's a politician. Here's a tip for Labour politicians. If you know that your party has been tarnished with a reputation for antisemitism, whether or not you think it's justified, try not to go out of your way to write an letter about how Jewish people's racism is different (let's be honest, lesser) to those of other racial minorities.
But also her argument is absolute bollocks. One could make the argument that white-looking minorities in the modern era, like Jews, travellers, gay people, etc, could fly under the radar by simply hiding their identity, whereas black/brown people can never do that. It's not a great argument, basically meaning that you're saying that not being able to openly live according to your culture without fear of attack or abuse isn't (technically) racism. But I get that some people might define racism as purely a colour thing, which is very much an academic argument - is racism just about colour or does it include ethnicity and culture? But that's not what she said. She said that 'there were no white-seeming people manacled on slave ships' as if there isn't some equivalency between that and the holocaust, which was explicitly about racial purity, and pointed to pre-civil rights America and South Africa, as if Jews didn't face centuries of similar segregation in many European countries leading up to the holocaust. Given that she's pointing to historical examples that are older than the holocaust, she is basically arguing that the holocaust wasn't racist prejudice, it was something different. Given that even if you believe that, it's such an academic and inconsequential distinction, why the fuck would you feel the need to make that distinction given that your party is trying to recover its image after being accused of antisemitism? For a politician, she just doesn't seem very good at politics.