Harry Potter's unknown sister

The first night at Hogwarts

Italics=Mary thoughts

Mary POV

I walked down to a table that was blue and bronze and sat down near the front.

As soon as I sat down professor Dumbledore said let the fest begin. And out of nowhere food appeared! There was all kinds of food. The area I sat in was covered, so much food I thought I had never seen so much in my life. Slowly I started to put some bread on my table then I buttered it with the tiniest amount of butter as possible. After I had finished my two slices of toast I pushed my plate forward to say that I was done. There was no point in eating that as i will throw it up afterwards any way. Even if I did not want to.

Being the shy girl I am I sat done for the rest of dinner time twiddling my thumbs.

After pudding in which I had nothing to eat I waited for someone to show me my way. But all the teachers just left and forgot about me. So I went looking for my room on my own.

After a long walk I found a door that said the girls laboratory on it so I went inside and what I saw made me scared. I saw a girl in white with the Ravenclaw robes on. "Excuse me can you help me please I am lost and am looking for the Ravenclaw common rooms?" I whispered with my head hanging down.  "Well my name is Myrtle. What is yours?" Myrtle replied. "My name is Mary Potter. It is a pleasure to meet you Myrtle. "I said slightly lifting my head up.  "And I do know where the Ravenclaw common room is." Replied Myrtle. "Please can you show me? " I pleaded. "Of course"

Myrtle lead me all the way down to the Ravenclaw common rooms. Then she stopped.

Suddenly a voice spoke out of nowhere. What is the longest word in the dictionary?   After awhile of pondering the question I answered Smiles as it has a mile between each S.
Correct

Then it let me in. The common room was amazing. It is a circular room, with arched windows that provide incredible views of the Hogwarts grounds. There is also a statute of a person who looks important. And some tables and chairs in one corner and a lounging are in another. Looking around I notice a whole wall full of books.

She lead me up another stair case to my room. "Thank you" I said quietly. "Any time you need anything just come to me" she said and then disappeared through the wall.

I looked at the room and saw it had two beds in. I then realised that these beds probably were not for me. So I found a nice corner in the room and curled up there in case this was all a dream.

-----Dream-----
I was cleaning the kitchen floor when I broke the light Master was so  annoyed that he punch and kicked me so many times then he pulled out a wand and said cruico. It was awful. And it was a new way to hurt me. I was 5 at the time.
Then the dream turned into another time. This time I was 7 and Master tied me up for no reason and started to cut my skin.

-----Meanwhile-----
Dumbledore POV

I called a meeting after the feast so it was a case of finishing food and then leaving. To find out who the little girl clams to be. We found her birth  certificate and what we saw shocked us all. 

"Name: Mary Lily Potter
D.O.B: 25 December
Godparents:
Severus Snape
Remus Lupin
Minerva McGonagall
Parents:
James potter
Lily potter (nee Evans)
Siblings:
Harry James Potter (older brother)"
I read all of this out loud. "What" both Severus and Minerva said at the same time. "You are her godparents as well as Remus. She is also Harry younger sister." I said slowly "she is a Ravenclaw?" Flitwick asked. "Yes she is"