Some of this depends on the type and size of school, as it's different having your own locker and staying more or less in one place to having to go across a huge site in the pissing rain nine times a day. And whether she has a car.
Her own set of whiteboard pens, pencils, sharpener, ruler, glue sticks (they dry out very quickly, get Pritt Stik and keep it at home or in her handbag at all times), decent biros in different colours, nice notebooks, A4 pad, good scissors (do not lend or leave on a desk), Post it notes (square size), sellotape, highlighters, a good stapler and three boxes of staples (write the type/size on a label and stick it to the underside and write her name on another and wrap it round the top of the thing) and a foolscap boxfile for keeping these things in and hidden without having to rummage around in the depths of her bag.
A bag that fits an A4/Foolscap Boxfile and can be slung over her shoulder whilst carrying 30 other things through doors that are always annoyingly closed.
A laptop bag that is padded and can be slung over the other shoulder.
A really good carabina and keyring loops for the thousand different keys she'll end up with, her door entry card (label it with her name), her ID card and NEVER put them down.
A box of Avery L7161 or L7162 labels. Keep well hidden/only carry a couple of sheets in the boxfile.
A personal A4 papercutter and laminator. Don't bring them in, or they will be 'borrowed' and most likely broken if they ever find their way back to her
Cushioned insoles. And blister plasters. And shoes that are cushioned, well fitting, supportive and polishable. Spare tights in a high denier or packets of popsocks (bare feet in shoes can get rather sweaty when the caretaker turns the heating on three days into icy, wet weather but then takes over a fortnight to switch it off once the heatwave starts two days afterwards). A bar of soap/travel size wash is good for a quick freshen up.
A large diary. Things might be done by Outlook, but it's a lot easier to remember things if you write them out yourself as well.
An insulated water bottle with a carabina so it can be attached to her bag.
A smart blazer for the inevitable 'need to look smart for this unannounced visitor' moments.
An easily managed hairstyle/bands.
A can of dry shampoo, a spare brush and a lipgloss to be used when it's got quite frenetic and she needs to just reset.
Antibacterial hand gel. A handkerchief. Box of tissues. Spare sanitary protection. Paracetamol. Nail file.
Any particular herbal teabags, tea or coffee she likes - don't rely upon what's in the staffroom or leave any of it in there. An insulated lunchbag and box. Her own non dairy milk if she uses it. High Protein Snack bars. Emergency chocolate. Multivitamins and extra Vitamin D. Sunblock Moisturiser to go on each morning, just in case she finds herself on playground duty in an unexpectedly sunny half hour.
A warm, waterproof, midlength coat with hood for playground duty/fire drills/alarms. An umbrella to keep only for work in a locker/the car. A good, warm scarf and gloves.
A spare charger and two long USB leads for her phone.
If she has her own mug, as with almost everything else, it will be used by somebody else and disappear.
Not every school has the money to provide everything she needs - and places like that always mean some staff develop a fluid approach to the concept of private property, never mind the students.
ALWAYS set up a track my phone/laptop app and use a code lock. NEVER leave your bag unattended, thinking it'll be alright.
The mindset that it's supposed to be hard for the first couple of years and it will feel too much at times, but that's when any plans for selfcare prove their worth - holidays/weekends away, a perfectly clean home to come in to, bubble baths, a life outside school. Always maintain a life outside school, even if it's just a rule that one day each week involves spending 30 mins outside.