She really is beautiful! I love black cats, too.
Keep up the good work. When mine were younger and had excess energy, I would take an old tube sock and stuff it with batting/catnip and knot the end. They would wrestle and kick at that thing like crazy. Maybe you could try one without the 'nip and toss it close to her before you leave. I really think it's possible she is bored and has too much energy. In that pic, she has what I call "a boo face" - ready to go off. Whether it's fear or energy, you need to try and redirect it away from your body parts.

That really is heart-breaking about your friend and his family. They are in my prayers.