Why do people lie? Because they know they are in the wrong and don't want to get into trouble.
So, try to hang fire on your own initial reaction of 'argh ffs dd not again' take some deep breaths and say something along the line of 'Kid / dd/ <insert nickname or term of endearment here> we need a talk, you have five mins to make a space for me to shove my backside on your bed and we're having a chat" keep your voice light, but firm, no anger even if your feeling monumentally peeved off.
Give her five minutes and then go and sit on her bed, make yourself comfy and start talking. Start with asking if she understands that when she says 'no' or 'you think' or 'whatever mum' or whatever rude word / phrase / behaviour is inappropriate and unpleasant.
I'd trust her answer with this, and my guess will be a resounding 'no'. (My dd has SEN, she masks a massive amount and copies / absorbs how she thinks she should behave/ respond.) explain how tone of voice and words can be conveyed as being rude / aggressive and go through different scenarios with her.
Hygiene, if she has a laundry basket / bin in her room remind her to put all dirty clothes in there, and you'll need to prompt her daily to use it. You'll also need to prompt her to either put a wash on, or give it to you to wash. Tell her any pants left with skidders on the floor will get binned and she'll have to buy her own pants, if they get into the laundry basket she'll have more money to spend on clothes / makeup etc. you'll need to see this through, and be prepared for the meltdown when she realises she has no pants! Harsh but very effective! (Obvs keep a new pack in your room just incase she runs out on a school day!). Don't make an issue of the skids, she can't help it, it's not an act of defiance, just shove them on a hot wash, and maybe think about leaving a landing light and bathroom light on over night if she’s freaking about using the toilet at night.
My dd has a laminated chart of jobs to do before school and after school eg morning, brush teeth, brush and tie hair back, make sure all uniform is correct (because my dd has quite a few difficulties she has a clean shirt, trouser, socks and pants hung up (I was hugely relieved when the school had a new head and the tie got ditched and the uniform, apart from the fleece, was made generic), it meant we could afford a clean shirt and trousers for each day of the week...again only because dd has difficulties (ds just has two sets as he uses deodorant so never stinks and rarely drops food down himself)
Deodorant wise, my dd has numerous allergies so she can only use 'rock-pit' she doesn't like the feel of it (sensory reasons) but we've talked a lot around not stinking, as it's very unpleasant for everyone around her, and she risks being bullied, missing out on friendships. The deodorant isn't 100% effective, but it's better than nothing.
Hair washing and brushing was a massive issue with dd, but we went shopping for a shampoo and conditioner she really likes, a hair turban, a big soft towelling dressing gown, and a stupidly expensive but very soft hair brush, which has really helped. It might sound daft, but it has made a difference, obviously might not with your dd, but it's finding something which helps encouraging personal hygiene.
Do you reward her for good grades / behaviour / attendance? I appreciate money might be tight but can you suggest Saturday/ Sunday xx amount of time is study time and then reward both kids with a £1? Or offer a £5 if the end of term 'report' is good (my kids school do a grade 'summary' at the end of each term with a detailed report at the end of the summer, I know schools are all different so you may not get any info until the end of the summer term).
The eating; she might well have sensory issues around tastes, textures and smells. Encourage her to help you in the kitchen, encourage her to choose dishes she likes, and prepare them with her. We had a rodent nightmare so now have a very strict rule of no food to be eaten anywhere other than round the kitchen table.
If she does have SEN she may be the chronological and physical age of 14, but is likely to have a much younger cognitive age, so you need to role back the parenting to a younger age...it's really hard and it sucks. Having one NT and one ND kid the parenting of my ND dd is bloody hardwork, and sometimes I'd just like to cry and scream 'screw you autism and just fuck the fuck off'. But then I remind myself that I love my dd, and although at times it's hellish and I'll be honest and say a very very small part of me envy's my friends with NT kids, I'm lucky to have her.
Tiredness / hunger / over stimulation and illness hugely magnify my DD's difficulties, so I keep to very strict routines, even though at times it's a pain in the arse having limited flexibility during the weekends and holidays.
Oh and DD's primary and secondary school were clueless with recognising her difficulties, like your dd, my dd was / is quiet, shy and had no behavioural issues at school (actually she did, but they flew under the radar in comparison to the mega disruptive kids). Just easier to give detentions for PE kit omissions/ not having the right resources etc etc. than looking into difficulties with organisational and time management skills.
It is really hard OP, and it's just trying to find things which work. A few years back Another poster on here recommended the book 'just mum and me' published by American Girl. I'd highly recommend it, it definitely helped my relationship with dd. I also purchased the 'all about me 2' American Girl which deals with hygiene, health, and keeping safe. It's aimed at slightly younger teens, but I'd just put it on her bookshelf / desk or whatever surface is available in her room, and leave it for her to browse, she'll almost certainly think it's 'lame' but she might flick through it and find it helpful.