I think she’s immune from an in-party challenge for 12 months after surviving a Tory leadership coup late last year.
I don’t think that’s the same thing as a parliamentary no-confidence vote, which would spill the Gov and all parties could then form coalitions to try to establish a majority. I think. I’m not claiming to be across all this.
Edit: I’d assume that the Tories would still have the numbers with DUP support. But again, I don’t know.