The most worrying thing was how wrong the figures she quoted were. Some were orders of magnitude out from figures that would make sense, but she still said it. It’s all very well not knowing every single figure you might be asked about, but you need some common sense. There has to be a part of your mind that says “the figures you are about to quote can’t possibly stack up”.
£300,000 cost of 10,000 new police? Then £80,000,000 cost of 10,000 police? Neither figure is anywhere near plausible and someone at that level should realise that long before they engage their mouths.