You have to let her be able to hide. Maybe make her a cardboard box and cover this with some thick fabric to dampen the loud noise. Normally cats get over it quite fast after the noises have stopped (at least my cats have calmed down rapidly).
A cat will normally be more scared the first time this happens and it can take some time before she comes out of her hiding place.
Some vets give medication to cats before the noise starts (here it is new years eve). My vet gave me a pill for my cat but this made my cat lose control and made it harder for my cat to cope with the stress. I am not saying your cat will react negatively to medication but mine did.
When the fireworks start my cat hides under my bed and usually comes out about 10 minutes after it have stopped.
The most important thing is for you to stay calm and relaxed and let your cat hide and not force her out of hiding. She will come out from hiding within 1 hour after the noise stops normally.