Hi Mehvish,
Since your mom is still having menstrual periods, some fluctuations in her platelet level can be expected. I wouldn't worry about any of her lab results.
Low vitamin D levels can contribute to bone loss because vitamin D helps regulate calcium. The vitamin D will help. Another supplement that can help with muscle weakness is CoQ10. She should see improvement in muscle strength using 30-60 mg of CoQ10 daily. A good multivitamin can also be helpful.
If your mother doesn't notice a flare of symptoms from heat or sunlight, then sitting outside in the sun is a good idea for increasing vitamin D. If she avoids the hours between 11am and 2 pm when the sun is hottest, she should do fine. Tell your mom I wish her well. Best, Elaine