I can just about imagine a situation where the ERG forces her out in an attempt to get No Deal and she revokes out of spite to prevent it or something. The very last card she's got to play.
I think revoking might need an Act of Parliament, similar to how invoking A50 originally needed one so government had permission to do so. Though it might be something the Supreme Court would have to decide on first.
I can just about imagine a situation where the ERG forces her out in an attempt to get No Deal and she revokes out of spite to prevent it or something. The very last card she's got to play.