Her usual kit of meter, strips, insulin pen, needles, a small sharps box or similar, and some hypo treatments - whatever her usual is whether gluco tabs or lucozade sport or whatever. Small snacks for post hypo. I would also make sure she has carbs and cals or similar on her phone. Make sure school is aware she needs a phone with her (if that’s what you’ve decided). And I would put some gluco gel in her kit and check that it’s on her plan so someone knows it can be rubbed on the inside of her cheek if she can’t swallow. I wouldn’t do glucogen as it needs to be kept in the fridge and an ambulance should be called if she’s unresponsive at school anyway.
It may be worth getting her a medalert bracelet or necklace and making sure her emergency details on her phone show that she is type 1 diabetic (I can give details of how to put that on the home screen or emergency screen if you want)