Pants,
tights,
thick socks,
leggings,
trousers/sweat pants(not jeans)
vest
t-shirt
long sleeved t-shirt
thin jumper,or(micro fleece)
cardigan,or(micro fleece)
thick jumper, or(thick fleece)
coat, or puffer gilet, with waterproof, which helps keep wind chill out, waterproof trousers will keep her toasty.
Hat that covers the ears, scarf, gloves, wellys.
I doubt they will sit still, just layer her up so she can take things on and off easily, send lots of carb snacks,hot soup in a flask.
Honestly it really good for children to be outside, it is dangerous to install in them it should be avoided.