She is wearing the Ciao Lucia Allegra Top in the Shell colour. It is available for $285.
Margot also carried a Chanel camel coloured trench coat, that is no longer available for sale. You can however find a pre-owned version for £2,894.35 on Vestiaire Collective. Thank you @kristenjstewartcloset for this ID!
Wearing a pair of jeans that she last wore for interviews during Mary, Queen of Scots promotion, Margot re-wore her pair of Levi LMX X Shopbop Splice Flare Jeans in the colour Paradise Blue. Unfortunately they are now out of stock.
For footwear, she is wearing a pair of Vince Camuto Jendeya Convertible Studded Loafers in Black. These are currently on sale for £60! Once again she is carrying her Chanel Calfskin and Gold Tone Metal Backpack.