You can use a second piece of fabric to tie around her body to keep the arm in place. The fabric would be horizontal, and go around her back, go over the arm with the sling, and under the arm without the sling. Then just tie it in front where it won't bother her. This is how I learned to do slings when I was a Med Tech in the Air Force, and it does work well. She won't have tons of mobility in her arm, but she will heal quicker, be in less pain, and will probably still be able to use her hand. Also, make sure the sling is supporting the elbow so it keeps the pressure off of her shoulder. If this is unclear, e-mail me and I will try to send you a link of a picture to show you what I am talking about. Good luck and God Bless!