What is the ruling on a cousin working in a shop that rents out wedding and party dresses, knowing that most of the dresses expose the shoulders, neck, and chest, and are rented to veiled, niqab-wearing, and unveiled brides? Is it permissible for her to continue this work until she finds an alternative if it is haram?

It is permissible to sell and rent clothes that expose 'awrah (parts of the body that must be covered) and reveal charms if it is highly probable that the buyer will use them for permissible purposes. However, it is forbidden to sell or rent them to someone for whom it is highly probable that they will use them for forbidden purposes, such as wearing them in mixed gatherings, as this constitutes aiding in sin. If the buyer's intentions are unknown, the default is permissibility, and the sin falls upon them if they use the clothes for unlawful purposes.