GCSEs then the next excuse will be a-levels and then that they're doing their degree...
Ohhhh no no no no no!
Has she EVER helped around the house/been responsible for her own chores?
I'm betting she also gets an allowance/pocket money, phone paid for, Wi-Fi, Netflix etc etc ?
Has she EVER had a paid job?
I may be becoming an old fuddy duddy but I am beginning to think a big reason teens now are more lazy and selfish is because the laws around part time jobs are so strict it's virtually impossible for them to get one!
Having a job really rubs the corners off!
However it's also lax parenting I think in a lot of cases, you need to start young and keep it up!
I raised dd as a single mum since she was a pre-schooler.
Initially I worked full time, then I went back to uni, then I worked full time again for a bit until an accident left me disabled and unable to work.
Partly because being a single mum is knackering and busy,
Partly as I believe a parents job is to raise a child so that at 18 they are confident, capable and practical people ready for the adult world!
Dd was expected to pull her weight with age appropriate expectations from as young as that! Starting with putting toys away at end of day, dirty clothes in hamper, carrying her dirty dishes to the sink. It's very much a game at this stage and of course you need to not worry about them doing it "right" every time etc.
As she got older she took on more and more responsibility.
It also meant I was teaching her more - cooking and baking (which also includes food safety and minimising food waste etc), laundry (from sorting to drying and ironing/putting away), how to clean different surfaces/materials, how to do basic/minor maintenance (change a fuse, paint a door, use polyfilla), "make do and mend" especially when it came to things like clothes (taught her to take up hems, sew on a button, altering/upcycling older items) etc
By the time she was 16 I could have left her with a weeks worth of grocery money and in practical terms she'd have managed fine! Not saying on a mental/emotional level but definitely on a practical level.
At 18 she was working full time and moved into a place of her own nearer work (shifts so was a lot easier for her, but I think first serious boyfriend around this time was also a factor)
She's now at uni after taking a couple years out to save some money and she's kinda the "mother hen" of the group.
At almost 16 seems to mean you've left it rather late to address this and that means it's not impossible...but it will be a lot harder!
I've seen this with peers of dds the parents let them crack on until about this age and then suddenly expected them to do a load more at home, get jobs etc and because frankly the kids had been pampered there was conflict/friction.
It's much easier if it's done as a gradual and natural progression of parenting.
You're gonna have to sit down and talk to her and explain that you are not her personal maid!
That she is now old enough and more than capable of at the very least (I would say)
Sorting her own laundry (and not being wasteful by laundering things that haven't even been worn! Both financially and environmentally)
Keeping her room clean and tidy
Doing at least one regular (at least weekly) chore that benefits the whole house
Clearing up after herself if she's made a mess outside her own room (disposing of rubbish, washing dishes or at least putting in dishwasher if you have one)
Cooking at least one family meal a week - and I mean proper cooking not a ready meal!
To be quite honest I'd be saying she needs to find a part time job too. At this age stage things are about to get VERY expensive in my experience. She is going to want more money for social activities and clothes and maybe even driving lessons when she hits 17.
There can be SOME element of negotiation but decide what your boundaries and expectations are and have sanctions decided too (reduced/withheld allowance, removal of screen privileges, removal of phone, grounding everyone has their own things that work with their dc - eg my dd couldn't care less about screen stuff. But she hated being grounded!)
Don't paint yourself into a corner when instigating sanctions, start small...so if she pushes her luck you can increase the sanction!
So don't go all "right that's it your grounded forever and phone and pocket money everything is gone" (tempting though that can be at times! 
)
Mum - Ok well that's £1 off your allowance
Dd - That's not fair! You can't do that!
Mum - and that's another £1 for backchatting!
Dd tends to got mute at this point usually
See what I mean?
My own dds room did at times resemble a hellmouth! If it wasn't clean and tidy by 8pm on a Friday no allowance Saturday when she wanted to head into town shopping/bowling with friends!
Rest of the time close the door and liberally apply air freshener! (Esp with boys! What IS that?! My brothers room I swear it hummed it's stank that much!)
There were dramas along the way (the incident where she dyed all her school shirts pale blue by thinking she could skip the sorting of her navy school jumpers from the shirts come to mind! ) at which point I introduced her to colour run remover and whitener and she would speak of them to her friends as if they were literally magic instruments!