Speaking as one who has PD, I can tell you that, at least in my case, stress or upset can, indeed, result in intensified tremors. That said, only I am responsible for the way I feel, no one else is - I don't care what anyone else says or does around me, my feelings are MINE, to control or not as is my choice. It would be grossly unfair of me to blame someone else for the way *I* feel! If the way I feel impacts the way my body reacts, then I need to take a deep breath, calm down, do whatever I need to to get over it, I can't expect the whole world to change because I tremor if I become upset. Moreover, I would not think it is for you to stop calling or being around her for fear of her disease... if you are that much of a stressor for her, she needs to decide if she wants to be around YOU! At the end of the day, if I start telling people that their behavior or the things they say MAKE me tremor, then all I'm doing is using my disease to control the behavior of someone else - not fair, and the recipient of such unfairness should wave the BS flag right away!
You might try asking your Mother to tell you politley, when you are talking about something that bothers her, that she would rather not hear about it. Tell her that you will be glad to change the subject and keep that topic off limits for the future, but that you are not responsible for her tremors and will not be blamed for them because it is simply not fair.
Well, good luck - and, hang in there, you'll work it out.
Kim