Bullying housemates - ignoring me

I recently moved into a houseshare with 5 other girls, I had known these girl for a few months prior and it was my understanding that at least 1 of the girls didn't know the others so I wouldn't be the only one who was sort of out of the group anyhow this was not the case. From day one I felt the sense of being left out and excluded. I have since really tried to be included, which is hard when plans are made without noone telling me and going places almost secretly.
I took over from a girl who backed out of the house from them very last minute, this should have been a little bit of a red flag, I know people who used to be friends with them until recently and have all said the same stuff, and have told me how sorry they feel that I have to live with them. Besides the uncomfortable feeling of being excluded I put it down to just getting used to each other as they most of them have known eachother for years and everyone was still moving in. I noticed small things to begin with including small silly digs about things that I won't go into detail about but I brushed it off.
However, one flatmate in particular has made my life a living hell - I have never felt so anxious in my life and feel like I'm constantly about to have a heartattack from the stress and anxiety. It begun when she started ignoring me, completely out of the blue, I'd say hi as we passed in the hallway and I'd get no reply. I thought maybe she didn't hear me, so I started saying it louder when I saw her and this is when it was confirmed that she was blantantly doing it on purpose. I began giving her the same treatment but noticed it proved more stressful for me. She is more than chatty and lovely to the other housemates. I had a friend over for a few drinks, who she knows, when I left the room she did not say a single word to him - but when the other housemate came in she was eagerly chatting to her, my friend told me this once we left which being honest made me feel a bit embarrassed about her rudeness.
The other day it just confirmed my thought of moving, I hear her come up the stairs so I step aside on the small landing at the top of the stairs, she walks straight past me into her room, doesn't even look at me - doesn't even acknowledge me, literally like I was air. I know the other housemates and her talk bad about me behind my back, made every clearly when I walk in the house and they all go silent and stare at me as I walk in. I have also been told through friends of friends they have heard them talking about me in the club. I have been looking for studios and other accommodations for about a month now as I know that even talking to her will make the situation worse.
They make comments walking past my door, they're very sly with the comments so not straight up directed at me otherwsie I would say something. I dread coming back to the house and will spend all day out to avoid them. I guess what this post is about is has anyone experienced this situation? I understand they need someone to bully as which has been made clear to me, they are also constantly badmouthing their mutual friends and other people and I believe this is why the girl I replaced for the room had experienced. I am going to move out and aim to move in January, I hope the landlord will give me a compassionate leave, however, at the moment I am struggling to find available accomodation, but I cannot stay here. I know I have not done anything to deserve this behaviour, I am clean, considerate, don't make loud noises or bad mouth anyone, I more than contribute to household supplies which makes this situation more confusing.
Thinking back before summer we were supposed to all meet to get to know each other which she made impossible to do and over summer when I messaged her she never replied, I met her once at a social event and she didn't really talk to me then and then when we first met she didn't talk to me the whole night. I have spoken to friends and family about this which they find very odd as they know my personality and I very very rarely clash with anyone, they have put it down to some sort of jealousy which I - not to sound self-centered - believe might be the case. Why is she acting like this just towards me?

You won't like this answer - They do it because they can (The wholesale bullying is led by a sociopathic ring leader) Probably because you are seen as 'safe' and they can get away with it. Something makes you 'stand out' You will probably just be a kind, polite person and therefore an easy target.
Your only option is to hold your ground. Try not to second guess any reasons for their behaviour and certainly never let this nasty group get under your skin. Find somewhere else to live as soon as it is practicable.
Never give them a reason to hate you. It's easy to want to lash out. Just be pleasant and keep yourself to yourself. Be careful what you tell them because you can have it thrown back at you.
If you can get support from college or Uni - take advice asap and find as many people who can support you, emotionally, practically and physically if necessary in order that you can stay away from the house.
Make sure you get any electric or gas meter readings now and on the day you leave for absolute proof. Ditto photos of every room you have access to including your own and photos of any damage (and undamaged) Get copies of any contracts you have signed. You need to make sure that you will not be hung out to dry for damage etc when you are gone and at the end of the rental term.
You need to remember that there is far more to this world than one small group of sad girls all clinging to each other for moral support in a power game. They are nasty cowards. Don't give them your head space. Every time you let them get in your head you are giving them Oxygen. So be aware and don't do it. This is something you have control over.
Good luck. You have a choice - you can always change the scenery and it won't last a life time. When you shut your room door it is your space. Just don't let them dent your self confidence or play mind games with you. Don't let them change your outlook on others if you are kind and good natured. Find another pleasant group to get settled in with and you will find that happiness away from them. At the moment you are in the thick of it, like dropping in on a war.
I'm not suggesting in any way that you do this. Your own imagination can help you heal the hurt. Imagine you have bought a thoughtful leaving present (a piece of smelly fish - mackerel or herring or old meat. Imagine tacking it to the back of any communal picture before you leave. It would be even worse if you were to accidentally spill some milk on the floor. Stay sane, keep your sense of humour and don't get involved in their nasty games. Keep a forcefield between you and hold your head high.
There are so many millions of lovely people out there. Just a shame 5 are stuck in a small space with you.

Your life should not be ruined because of your flatmates. I had a similar situation and basically ignored the flatmates and invited my friends from outside of the flat whenever I could. Yes, I had the cold stares and had to withstand being ignored in the kitchen but - hell - I had paid an equal amount to be in the flat so I did not feel I needed to compromise and live like a hermit in my room.
Chin up and come out fighting. I know it will take a toll on your mental health but dont let them win.

This is awful, I think maybe try and find somewhere else as these girls are obviously not people anyone wants to live with.
Hope this works out for you

Your life should not be ruined because of your flatmates. I had a similar situation and basically ignored the flatmates and invited my friends from outside of the flat whenever I could. Yes, I had the cold stares and had to withstand being ignored in the kitchen but - hell - I had paid an equal amount to be in the flat so I did not feel I needed to compromise and live like a hermit in my room.
Chin up and come out fighting. I know it will take a toll on your mental health but dont let them win.