Given the link between certain sections of the Labour party, misogyny and anti-Semitism, I suspect it is because she's Jewish.
I actually do not think it is motivated by her being Jewish, but really 'just' by her being an outspoken woman who has expertise in the field, and therefore has credibility and great potential impact.
That said, considering how during NAZI rule Jews were forced to clean up streets on their knees with toothbrushes in public, and Jewish shop fronts were being marked and vandalized (including being pissed at, I bet) and the owners had to clean their shop fronts and doors afterwards, this leaves a particularly bad taste in my mouth.