Because she has never been elected to anything

Given that diplomacy is not necessarily best conducted by elected officials, I fail to see why this is a huge problem.

was never a particularly senior or influential politician in the UK

Uh... in my view, that's a mark in her favor, when one thinks about recent senior and/or influential politicians in the UK.

The brief was for a nominally leftist women to balance male right wingers in all the other EU leadership positions.

Ah.  So any woman named to this position would be a "token"?