I regret agreeing to live my 2nd year housemates

So the main reason is that two of the housemates currently live together in accommodation and their kitchen is a mess. I’m going to refer to them as A and B. So A claims that it is not them that makes the mess but they are the only one who cooks while B and the others in the flat typically eat takeout or ready meals. A’s room is also a mess and their sink looks like it could start a new deadly disease…
I’m not sure how to attach photos on here but to describe it: there is food and dust all over the floor, the bins are overflowing so much that they’re taking over the room, surfaces have food covering them and there are plates that havnt been washed in weeks sitting in the sink.
A also tend to think they are correct about everything (most recently they decided that they know everything about my home town which they have never visited) and my flatmates (whom they have never met - apparently the only reason my flat is clean is because my flatmates are scared of eachother??? not sure where that came from but okay).
They also make subtle jabs at my family. I feel that this is because my family is very different to hers as I have been fortunate enough to grow up in a nice area whereas she lives in a ‘rough area’ (her description not mine) and our families tend to do things differently. for example, my family don’t really drink so when I hear that their mum got so ****ed she had to be taken home from a family meal out, I was surprised but did not comment as it’s none of my business whereas they have implied that because my mum is a doctor; she has no sympathy and is an ‘almond mum’ (I have said nothing to make her think this).
A also insults my food and pulls faces even when it’s the exact same food that they made a few nights before. I am celiac so some of my food doesn’t look as appetising as regular food would and I tend to eat healthily. I may wrong but I feel that this stems from her being insecure as she is overweight and she has told herself that the only reason I am slim is because I don’t eat (I actually eat a lot as I am pretty active).
This has worsened over time as I typically get a lot of attention from men on nights out and the boys we are living with have said that they would not date an overweight person.
If it does stem from insecurity then I would appreciate advice on how to help her overcome this before it ruins our friendship.
B also goes days without sleep as they play games all night and shout at their computer. A also blasts music late at night.
A also likes to act like i’m dumb when I say something that she has a different opinion on. This is worse when we are with other people and they have a smug look on their face and they shut down my opinion in a condescending way. This is usually about insignificant things or them correcting me about a fact about myself (I would argue that I know what happened in my high school better than they do but oh well)
Side note: I can’t say much about the other two people we are living with as I have not known them as long.
I’m dreading next year
Any advice is appreciated

This sounds like a very toxic situation already and you are not even living with them.
If it was just that they were messy, I would suggest setting up a rota right from the start but this is more about how they behave towards you. This jealousy and putting you down is toxic and not something you should tolerate.
My advice is to:
Well done for being brave enough to realise it is not going to work.
Note: When talking to your parents and the university, don't bother talking about the mess. Tell them about what they say about you, your food, appearance, the jealousy. That is not a situation you want to live in.
Tell your parents, they will support you.
Good luck!

Thankyou for replying so quickly! The contract for the house has been signed so it will be difficult to get out of it and I don’t know anyone who will be willing to take my place. How should I approach this with the landlord?

Is this a tenancy that you are in at the moment or one that you signed to move into in the future? Is this private or Uni accommodation? To me it sounds like private.
See the Shelter website (housing advice charity) for advice on how to deal with flat mate disputes and how to end/transfer a tenancy as the landlord and yourself both have rights but obligations.
You could also get an appointment with your Student Union as they often have support officers with knowledge of housing law.
Your flat mate issues (i.e. breakdown in the relationship with your flatmates, their messiness) are irrelevant to the landlord as what you have is a business contract with them.
For the sake of playing devil's advocate, I will remind you that private landlords are not responsible for you wellbeing, welfare or the culture of the flat.
I also disagree with contacting your parents unless it escalates as it sounds like you are mature enough to problem solve this yourself and you have sources of advice and support. Think of this as a test of becoming an independent adult.

Is this a tenancy that you are in at the moment or one that you signed to move into in the future? Is this private or Uni accommodation? To me it sounds like private.
See the Shelter website (housing advice charity) for advice on how to deal with flat mate disputes and how to end/transfer a tenancy as the landlord and yourself both have rights but obligations.
You could also get an appointment with your Student Union as they often have support officers with knowledge of housing law.
Your flat mate issues (i.e. breakdown in the relationship with your flatmates, their messiness) are irrelevant to the landlord as what you have is a business contract with them.
For the sake of playing devil's advocate, I will remind you that private landlords are not responsible for you wellbeing, welfare or the culture of the flat.
I also disagree with contacting your parents unless it escalates as it sounds like you are mature enough to problem solve this yourself and you have sources of advice and support. Think of this as a test of becoming an independent adult.

Although the OP said their parents were paying the rent, they did not say that they were the guarantor (though they could be, it's not clear).
I would still recommend that the OP does her own research about the status of her contract with her student union rep and a housing advice charity before even considering consulting her parents.
At the age of 19, you can marry, vote, work, drive, have children, drink, and hold a tenancy in your own name.

This is not about ego, winning an argument or even questioning a 19 year old's abilities. This is about what is in their best interests.
Why would someone advise a person not to take advantage of every support available in such a potentially challenging situation? Bizarre.
I'm glad that they have decided to ignore the bad advice and instead speak to their parents.

In just over a year's time, assuming she is undertaking a 3 year degree, she will be applying for graduate jobs from the autumn of her final year where she will have to demonstrate communication, leadership, and problem solving skills to the recruiters.
Her mother was likely dissecting a cadaver at her age.
There is nothing wrong with her having a reasonable stab at solving this issue herself and presenting potential solutions to her parents after doing research. She is the tenant.
When she graduates in two years time, should she find her future work colleagues obnoxious and judgmental like her current flat mates, or has reservations about the terms and conditions of her work contracts like with her proposed tenancy, she will be more resourceful.