I can see her point. This way she doesn't have to face the electorate post-Brexit.
In 2020 we'd be a year post-Brexit and everyone could see how it was going to work out and, whatever the deal, she'd not win.
In any Brexit insufficiently hard to produce an economic disaster that would take at least a decade to climb out of she'd be hounded by the UKIP/Gove true believers for having been too soft.
Otherwise she'd have to face a large percentage of the population who'd finally be cottoning on to the idea that their jobs would be migrating to the EU.
This way she gets an extra couple of years to enjoy running her police state without having to look over her shoulder at the ECJ and, if she gets her way, the ECHR although that might be more difficult. About the end of March 2022 she announces her retirement and leaves someone else to sort out the mess.