I'm so sorry that your mother is dying.
I think times have changed. A dear friend of mine graduated from med school about ten years ago. Not only were they respectful, they had a memorial service at the end of the term.
Perhaps it would help to remember that your mother is doing this because she does not believe that her body continues to useful after death. I feel much the same way. At this point in time, I've only indicated on my DL to donate all organs and so on but not my body because my spouse is not comfortable with it. But I am. And if those med students say uncouth things and/or laugh, well, I'll be long gone, at peace, and my wishes will still have been respected as they will be learning.
Again, I"m so sorry.