She’s basically El Presidente now. In regards to Brexit she has presidential powers. It’s she, and she alone, who can agree a delay, or decline to agree a delay. She can ignore her Cabinet (which she has). She can ignore Parliament (which she has). She can ignore her party (which she has). She can ignore the party members (which she has). She can ignore voters (which she has). She currently has God-like powers, at least until December when she can face another internal party vote, which she could well win despite everything because everyone on her payroll gets a vote.
Even a Parliamentary vote of No Confidence in her government doesn’t necessarily bring her down, because she can still carry on as PM for 14 days, agreeing new delays, and if no new government is formed from the existing MPs in that 14 days, an early election is held. And guess who will be the leading the Tories into it? Theresa May again! Because even if she loses a Parliamentary vote of No Confidence, that doesn’t stop her being leader of the Conservatives. To someone in her situation determined to carry on, they can. There’s very little anyone can do to stop her, even if the whole country is against her. You’d have more chance of starting up a new party and trying to win that way than getting her out of the Conservatives.
But even if they did, she could still carry on. She can be PM without a party.
Update 2: I should qualify my claim that she has dictator-like powers. In many ways she’s powerless. She can’t pass any legislation by herself, including her own WA. And she’s only kept in power by supportive MPs. But what she does have is the ability to keep preventing Brexit indefinitely, and it’s very, very difficult to remove her.