She's doing what Sir Humphrey tells her she can do. These politicians pop over to Brussels now and again to give the impression that they are doing all the stuff, but it's Humph and his team of 1195 experts that are working at it full time, likewise with Juncker - they are just figureheads who are seen to be talking about it now and again between all the other business and long lunches...the Brexit Minister could be replaced tomorrow by someone you never heard of who has been say pensions Minister for six months. This new supremo could be in Brussels the next day "negotiating hard" on our withdrawal from the EU, having overnight become expert on commerce, customs, tariffs, defence, fisheries, farming and two hundred and thirty two other complex subjects...I don't think.
Something you'll never hear the Prime Minister or any politician say when asked a question "we don't know yet until we hear from the experts at the Foreign Office/Treasury/ Home Office" - even if they've only been in a job for a few hours they still have to give the impression that they are heroically doing it all alone, when in fact they do very little.
When you add up all the holidays, sorry "breaks" and the short weeks, short days, they don't have time to do much.