I first noticed the symptoms of PD in my mom 10 yrs ago when she was shuffling her feet and bending forward from her waist. Something we all noticed was that although my mom kept eating, even before any treatment, she was losing wt. If I didn't see her for several wks., then the next time I saw her there would be obvious wt. loss. in her face. Her PCP , who doesn't need to be treating people, didn't think a 30lb wt. loss in an elderly person something to be worried about. The neurologists haven't said anything about her wt.
She is now under 100lbs. Is there any way to stop the wt. loss? She's eating but she's just fading away.
https://www.agingcare.com/questions/stop-moms-weight-loss-177726.htm
You were encouraged to find her another doctor. Have you?
That being said, I would look into what she is eating and see about increasing the calories. Does she still live in assisted living? Perhaps she's not making it to enough mealtimes, or eating enough at each mealtime. If possible, visit with her at a mealtime and accompany her. She may eat better with you there. Find out if her teeth are bothering her. That can be a problem as our gums shrink. Find out what her favorite foods are and see that she is able to eat food that she likes. Maybe the food at the AL facility isn't to her liking. Use liquid milkshake type supplements. Use ice cream and other high calorie foods as treats.