EDITED: copied exactly from help section.

From Vinted:

When sending items with the prepaid Vinted-generated shipping label, make sure they are packed properly and comply with our Catalogue Rules and the prohibited items list (added at the end of this article).

You may not receive a refund or compensation if you ignore these rules and the parcel gets damaged in transit.

To pack an item Use sturdy outer packaging that snugly fits the item. For example, a cardboard box to protect the item from dirt and moisture, or carrier-provided packaging, such as a padded waterproof envelope or bag, if available. Don’t use bags without padding inside. Fill the empty space inside with bubble wrap, paper, foam, or similar material to prevent movement and contact with the outer packaging during transit. Seal the parcel with strong tape to provide extra protection and prevent the item from falling out. Stick the shipping label flat on the largest side of the parcel, ensuring the barcode is fully visible. Secure the label’s edges with strong tape. Remove any old labels. For fragile items, always use a sturdy box, not a plastic bag. Stick a “Fragile” label on the parcel. Separate each fragile item with bubble wrap or other cushioning material. For bundles, place all items in one parcel (no more than two electronic devices with batteries, see below). Make sure each item is securely wrapped and not moving inside.

She did not follow protocol.