I don't know her situation but honestly the best thing I did for my sister was telling my mum about her self harm. It took a while for her to find a therapist she liked (who didn't tell mum most of what they talked about) but she has found one who does cognitive behavioural therapy and it really helped. She is now more than 5 years self harm free. You are already doing a great job supporting her but it is a tough gig to do all on your own at 14! If her parents aren't going to be helpful I would talk to the school wellbeing/guidance counsellor if they have one. It's hard to see a psychologist where I live without parent's consent because of payment, but there are drop in places or phonelines if needed. Self harm can quickly get more serious if untreated so the root problem needs to be attended to.

I don't have an absolute favourite genre, but I've been reading some classics lately, and they're super good! At the moment I'm read The Picture of Dorian Grey, and I'm really enjoying it :)
Also reading Chalice of the Gods, the most (?) recent book in the Percy Jackson series. Really good, I recommend

Here's the answers you asked for! It's a bit long, sorry abt this :')
TO CLEAN A CUT:
Make sure your hands are clean (eg wash them or something), if it's still bleeding then put pressure on it for a minute or something (however long it takes for it to do its thing). Wash it with some water to clean it—you don't need to use anything big, like different antiseptics unless you think she's at a risk. Then put a plaster/bandaid/bandage on, and ta-da! You have yourself a clean cut.
TO CLEAN A BLADE:
Wash it with antibacterial soap (eg dish soap) and then use a household lubricant (WD40 is great for rust removal/prevention!). Scrub the WD40 on the blade to get rid of rust. Last thing to do is to dry it, et voilà. I do think burning works too, but this is what I do for my Swiss knife after using it for stuff, like cutting open stubborn food packages.
COPING METHODS:
I'm not super good at helping those in need (I'm in a stalemate myself, knowing several of my friends selfharm but not bringing it up bc they'll then ask me, and I'm not telling them I cut/have cut). One of them mentioned in a roundabout way that an alternative is drawing on your skin helps. I, personally, tear up A4 paper on a daily basis (I have no pages left in my copy) bc some destruction is being done, but it's not permanent/longlasting. The oragami is a great idea! Not only is she learning/getting better at a skill, but it could help distract her from self-harming. Another thing would be if you text her often, like at times she would be alone and have the opportunity to cut. Don't be too overbearing with the contact, just check in on her when she's alone.
HOW YOU CAN SUPPORT HER:
You seem like your super kind and supportive. I'd say be there for her, don't make every conversation abt her habits,, and continue your friendship as before.
ABOUT ALCOHOL:
You should encourage her not to drink, since it's bad for her health. You're more likely to become addicted to alcohol when you drink it from a young age than after 18. Ask her if she could at least cut down on the amount she consumes.
SHOULD YOU GET HER A THERAPIST:
8 honestly don't know. I think you should leave it for now, but introduce the idea to her again when you're both more comfortable talking abt it.
ARE YOU A TERRIBLE FRIEND:
Absolutely not! You're being very considerate and caring. Keep being your amazing self.
You seem quite self-sacrificing, so just remember to take some breathing space and time for yourself, aswell :)

Twas brillig, and the slithy toves
Did gyre and gimble in the wabe:
All mimsy were the borogoves,
And the mome raths outgrabe.

“Beware the Jabberwock, my son!
The jaws that bite, the claws that catch!
Beware the Jubjub bird, and shun
The frumious Bandersnatch!”

He took his vorpal sword in hand;
Long time the manxome foe he sought—
So rested he by the Tumtum tree
And stood awhile in thought.

And, as in uffish thought he stood,
The Jabberwock, with eyes of flame,
Came whiffling through the tulgey wood,
And burbled as it came!

One, two! One, two! And through and through
The vorpal blade went snicker-snack!
He left it dead, and with its head
He went galumphing back.

“And hast thou slain the Jabberwock?
Come to my arms, my beamish boy!
O frabjous day! Callooh! Callay!”
He chortled in his joy.

’Twas brillig, and the slithy toves
Did gyre and gimble in the wabe:
All mimsy were the borogoves,
And the mome raths outgrabe.

By Lewis Carroll

1. rocks, i suppose., 2. aesthetic stickers, 3. mint boxes (tic tacs and such), bottle caps/tabs.
the second question: 1 because SHINY
2 because aesthetic
and 3 because it’s useful

Postcards and pins. I've got a collection of postcards on my wall, and a jean jacket covered in pins.