Q #1: Yes, the lack of vitamin D, along with no loaded exercise would likely be major culprits behind the problem. CLO would be my preferred solution, at least 2000IUs a day, although her situation might call for more. Taking the CLO with some amount of saturated fat would also be helpful.
Q #2: Weight vest. Start with 1 pound, slowly work up. This can be done for periods during the day and/or during the exercises you gave her and/or her Feldenkrais (the added weight actually can improve one's feel in their exercises as long as it doesn't interfere with any movements). Doing weight vest walking combined with carrying some DBs (even adding some upper body movements) can help the mid- to lower spine regions, the hips/pelvis and the upper arm bones. See the recent neck strengthening thread for some ideas to train her neck (and thus the cervical vertebrae).