Can you try making a little ring to go around her neck, preventing her from reaching the wound? You could remove it when she is eating and drinking if it gets in her way. A Tee shirt made from a cut off sleeve of a Tee or sweat shirt might also work. The cuff should be around her neck. You can experiment with something that works. If a bandage works best, that might help. But make sure that it is covered with antibiotic ointment or wound cream. It may be irritating her, itching, or hurting. Have you ever located the sharp edge that cut her chest?