Hello Pipistar, I've both made and altered beaded gowns. The reasons for snipping the threads and removing the beads, rather than smashing them, are two: First, the shards from the glass beads cut threads of the fabric, especially sheer fabrics. Second, you will need to resew beads to any area that's visibly missing beads. While this might not be noticed on a costume, a gown is always looked at by other women. It's also good to keep them for replacement (I learned this while doing alterations in a formal wear shop. Most better RTW manufacturers attach a small bag of replacement beads for this purpose). I realize that she might never wear the dress again, but she might want to sell or give the gown to someone. Cordially. Nehmah