But then a talk radio host called Iain Dale asked her, live on air, the question she must have been dreading: Would she now vote leave if there was another referendum?
She couldn't say 'no' because she is leading the negotiations with the EU about leaving. She couldn't say 'yes' because that would be a lie. So she waffled and dodged.
Dale heard her out and then, very politely, asked her the same question again. She dodged again. So he asked her again. And again. After four goes, it was perfectly clear to everybody that she would not vote leave, and probably didn't in the first referendum either. It's hard being a politician sometimes.
The United Kingdom is now halfway out of the EU - or rather, May's government has now used up half the time that was available to negotiate an amicable divorce settlement and decide on the post-separation terms of trade with the EU, Britain's biggest trading partner by far.
Unfortunately, it has not settled half the issues that need to be decided, or even a quarter. Maybe one-tenth.
The delay is almost entirely due to the deep divisions in her own cabinet. Half of them are Brexiteers, some of them quite fanatical about the need to leave, while the other half secretly wish the referendum had come out the other way. And if they do have to leave, they don't want to go very far.
It's all about "hard" and "soft". The fanatics want a "hard Brexit" in which the UK crashes out of the EU without so much as a post-Brexit trade deal, while their opponents want to stay in the customs union and even the single market (where all the EU countries adhere to common standards for goods and services).
May couldn't afford to alienate either side by taking a stand because the consequent war within the cabinet would probably bring the government down - and the Conservatives would probably lose the subsequent election.
But if she couldn't tell her own colleagues which way she was going to jump, she couldn't tell the EU negotiators either, and so 18 months have passed with very little accomplished.
Now she has been forced out into the open - by the Irish question. The one land border between the United Kingdom and the EU is in Ireland - Northern Ireland is part of the UK and on its way out of the EU; the Republic of Ireland is staying in the EU, so obviously there will have to be customs posts and other controls on that border post-Brexit.
But there must not be that kind of "hard border" or the war in the North is likely to start up again. Part of the international peace deal that persuaded the fighters of the IRA to lay down their arms 20 years ago was the guarantee of a "soft border" between the two parts of Ireland, with no passport checks, no customs controls, no barriers of any kind.
Break that deal, and it probably wouldn't be long before the killing started again.
Theresa May couldn't go on ignoring this question because she depends on the support of a small unionist party in Northern Ireland for her majority in Parliament. In the end, she had to agree to what she called "regulatory alignment" between the UK and the EU in order to keep that border open.
For all practical purposes, that means the UK must stay in the EU customs union and internal market, although it will no longer have any say in how they are run.
This does reduce the whole Brexit enterprise to a nonsense - the UK will pay €40 billion in compensation to "leave" the EU, and end up approximately back where it started.
It's still better than crashing out without a deal, and it may be what May secretly wanted all along, but there is going to be a rebellion by the Brexiteers in the cabinet sooner or later.
So it's all up in the air again, really. "Hard Brexit", "soft Brexit" or even drop the whole idea and stay in the EU. It was always a stupid idea.
■Gwynne Dyer is an independent journalist whose articles are published in 45 countries.
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