Spoilers for むらさきのスカートの女:
While the fact that the narrator was working at the hotel was revealed quite late, I wouldn’t call it a twist. And it wasn’t the point of the story. You say that the “woman in purple just disappears like an ass” but why? She owed the narrator nothing, and wasn’t even aware of her presence most of the time. She has been seen throwing someone to his death (she thinks), is given money and a way to escape, she takes it. She has no reason to follow the instructions of some random person who just happened (for all she knows) to be there with a plan. If I were purple skirt woman, the narrator appearing like that and claiming she had a carefully thought out plan would definitely freak me out.
Then the major twist for me, was the ending. The narrator seems to entirely take purple skirt woman’s place, sits on the same bench, behaves in the same way. Maybe it’s a cycle? Maybe she will get stalked now? Were they even ever two different women? And if she was quite as crazy as she seems at the end, how much of what she told us can we really trust?