Parkinson's disease is not infectious. My husband has it for 12 years, I'm his sole caregiver and I'm fine. Parkinson's is described as trembling, skaking when the hand, leg, foot, etc is not being used but is at
rest . If she shakes when using her hand it may be Parkinsons' but not likely. If she rests her hand on her lap and it shakes then it could be Parkinson's. There are a lot of diseases with similar symptoms. Unfortunately I don't think there is yet a positive test to tell you yes or no.
The other symptoms develop later. Some go years with no symptoms. I wouldn't worry too much until you know. When you do find out, even if she does indeed have it, she may still have many good years. Good luck.