OP - I'm sure that was very difficult to do but I'm glad to read that you did it. I lost a baby after 40 weeks and my brother did this for me before I came home from the hospital and I could not have been more grateful to him for doing that. He took everything to his house and my husband, who did want to go through everything to say goodbye, went through it there. We all grieve differently - some people suffering this kind of loss find therapy helpful, others don't; some find stories of others helpful, others do not want to hear them at all.
Please don't worry about what your sister "should" do to move forward - just stay close and listen to what she says she needs and wants. You could also do research on resources (support groups, therapists in her area specializing in baby loss, etc) that you can share should she want them so she can access those if she feels she needs them. This is a devastating loss - and with the hysterectomy, it's really two losses she is grieving. A good resource if you haven't found it yet is
http://www.glowinthewoods.com/.
I'll be sending thoughts of strength to you and your family.