Hi, I understand quite well your concern. In your case i suspect that two possibilities can cause these vomits: 1. Levodopa (you haven t mentioned what kind of treatment does your grandmother take, but levodopa is the gold standart of the present therapy)The most common side effects are nausea, vomiting, low blood pressure, involuntary movements, and restlessness.The nausea and vomiting caused by levodopa are greatly reduced by the combination of levodopa and carbidopa which enhances the effectiveness of a lower dose. 2. Inner ear. Some neurologist believe that parkinson disease can affect also the inner ear and symptoms can include vomits, nausea, diziness, vertigo etc. So, I suggest you to see your neurologist again and tell him these two possibilities, in order to get the adequate treatment. Hope I ve helped you Dr. Ermira Biu