This is a difficult situation, as I agree with you about your mother being at risk for "choking". Have you asked your mother why she doesn't like anyone to watch
her eat? Was she like this before the strokes? Perhaps she feels like her eating is something that she can still control herself, and that is why she doesn't want you involved. The best thing for you to do would be to make sure you are giving her all the tools to make her eat as safely as possible. Remember, that even if you are standing right next to her, she could still choke. The best ways to decrease the risk of choking would include:
1) Have her eat up in a chair: I do understand that you prop your mother up in bed, which is good. However, it would be better if she ate when sitting up in a chair. This would be the best position to help decrease her aspiration risk even more.
2) Have her seen by a speech language pathologist: These are specialists that can assess your mother's swallowing to see if she needs any special diet to lessen her risks of choking/aspiration.
3) Occupational Therapists can work with her to find utensils/ adaptive equipment to help her eat better.
One other thing to keep in mind is that with her history of strokes and Parkinson's disease, she is actually at risk for something called "silent aspiration", which is when little bits of food and fluids can go into the lungs silently (there are no choking sounds at all when this occurs). Therefore, while I appreciate you wanting to watch over her while she is eating, it will not help her swallow her food any better. I think if you get the specialists I have listed above to check her out, this will be the best way you can help her eat more safely. Good luck!