The day Luna Lovegood got zapped from the timeline and into the one Harry Potter knows as real started with a detention she was serving. It started with the teacher supervising her lacking anger and being filled with pity. He knows that it's not her fault she is there. The school system was not built for everyone. Luna included.

Luna reads instead of writes. In this world (our, Reader, world), there is no magic. There are no Nargles, or Wrackasuprts. There is just detention, where Luna is supposed to write lines not in blood. 

But Luna (who, in the reality she calls home and the reality that is, for lack of better word, 'canon,' is called Polly Smith) does not feel like writing. And her teacher does not feel like making her. So instead she picks up her book and reads. It is titled "Harry Potter and the Deathly Hallows," and she likes it a lot.

At the end of chapter thirty-four (where our dear old Harry Potter dies), Luna Lovegood pops into Harry Potter's world. It feels like a Tumblr prompt. It feels like plot convenience. But she takes to the name Luna Lovegood rather well -- even if she is regarded as an outsider, regardless of the world she resides in. Her powers, her foresight, are real. She sees time as a river, branching off only to reconnect again later on. She sees the future as it can be, but she knows that the world she now lives in is the world of the books she used to enjoy so thoroughly. The future, as it will be, is Everything Up To Chapter Thirty Four.

Luna can change it. Harry does not have to die to slay Voldemort, not if she has anything to say about it, and she may. So when another plot device, the things she hears and does not mention to others, tells her of a certain spell and that her former principal is here, too...

Well, she knows what to do.

The day Dolores Umbridge (known in our world as 'a bitch' but formally going by the name 'Susan Scott') comes into Harry Potter's world is one filled with coincidence. It is one filled with threats and presents, all of which she was prepared for, because she had asked for them, hadn't she? And as a God, she will always get what she wanted.

But it is not her will that has pulled the waves of Fate. It never has been. What she asked for and what she received line up merely by chance.

She asks to change the world she lives in... and it is merely chance that such happens. She fits the name Dolores Umbridge, surprising to no one, well. She plays out her little power fantasy, becomes controlling beyond control just because she believes she has the right so.

Dolores Umbridge might recognize her old student, Loony Lovegood, even subconsciously, so her punishment is to be expected, if unwarranted. 

Susan Scott and Polly Smith awake in a world not their own. But they will not be returning, so I suppose the focus on their past is nowhere near important as the focus on their future.