Upon resigning, a PM is by convention asked by the monarch to recommend a sucessor. That's how Eden, Macmillan etc got the gig.
If May plays ball, she would recommend the cabinet's choice, which on the face of it would be Liddington, Hunt or Gove.
So Betty, who's done this before, sends for the recommendee and asks, "Can you form a govt?" To which, they might say, yes, for a while maybe.
Then we have the prospect of a true minority govt, which might well not last long, and hey-hoe, it's general election time, Brenda.
"What? A Nurther Wun?"