I have sensitive ears and use hearing protection a lot. The best kind I have found is the soft, waxy substance that comes in a flat plastic box of little white or clear balls. Mack's is one brand, and I've seen generics. You can probably buy them at any chemists, though a big chain might be safer.

They are good at blocking machine noise yet allow a person to hear speech and music. On long plane flights, I put them over the ear opening, put headphones over them, and listen to music on my portable CD player.

Be sure she reads the directions and understands how to mold them to the outside of her ear opening.

On this page they are the box on the upper left:

https://www.macksearplugs.com/product-category/travel-ear-plugs/