Once she arrives at the bloody crime scene, things seem to play out as usual: she sees her father dying (although she has a déjà vu of the original Peter Abernathy, not the creatively mustached replacement), she gets menaced by a thug (this time it's Rebus, a puzzle in robot form), and pulled screaming into the barn.
Only this time things go differently. Time blurs. She finds a gun in the hay. And then she hears someone with a gruff voice -- it's no one we've met before: not Bernard, not Ford, not the Man in Black -- say the magic words: "Kill me." And it's like a gun goes off in her head and her hand. The loop broken, and Dolores made into a two-faced liar, she bolts into the night. But to where? Yes, she falls into William's willing arms in the final scene. But it's not entirely clear, due to her flickering memories, if this is happening in the same timeline as the one in which she fled.
I have a crazy theory about what might might be happening, the kind of theory that could only be written by a sleepless zombie at 5:14am after literally 20 straight hours of mainlining Westworld. Dolores said to Bernard, "There aren't two versions of me; there's only one." Every memory Dolores is informing every version of Dolores that is having it, past and present. Once she learns that, and how to master it, time will no longer be a tether for Dolores; she will not be stuck in a loop.