May is a shrewd politician. She knows that the opinion polls predict a landslide for her if she went to the country now. She also knows that opinion polls can be wrong. But the reason that she would be taking a terrific gamble (and she is not a gambler) is that an election fought now would become a second Brexit vote.
With the vagaries of the first past the post system, a coalition of outright opposition to Brexit, (the Lib Dems and SNP) and those opposed to hard Brexit (Labour), would be very likely to win a majority of Commons seats. There is, or was, a majority to leave the EU, but never to leave the single market and the customs union. Only a minority of ideologues actually want that and it is to that her government is effectively committed. May knows she won Copeland where Brexit was not really a feature, but when it was, Richmond Park, she lost fair and square a very safe seat.
Rather than a big majority, as promoted by those advising her to repeal the fixed term parliament act so as to be able to ask for a Dissolution, she could well end up without a majority relying on the likes of the Democratic Unionists or even UKIP. Or be excluded form government altogether. This Blog cannot predict that she will stay put and soldier on, but certainly speculates that she will. She is also haunted by the fate of David Cameron, who thought he was sure to win the fateful referendum.