Welcome, apolline; we are glad you found us and have joined us. I admire your willingness to be supportive of your sister.
As a person with MS, I encourage your sister (through you) to find compassionate doctors, establish a baseline with a thorough physical exam and MANY blood tests (including cortisol test, tests for all thyroid hormones, fasting blood INSULIN test, test for vitamin D level – get to know jimmylegs here; she has good suggestions for other tests), and keep copies of all these test results in her own file. I urge you and your sister to eat a healthy diet and exercise as possible – a healthy lifestyle is important.
Try to remain optimistic – most of us here think the answers to MS will be found soon. Ask any questions; most of us are not scientists, but we are willing to share our ideas. All the best to you and your sister.