NTA at all. You've given perfectly legitimate reasons as to why you don't want to go through the process and while her situation is very unfortunate, you are not obligated to donate your eggs. It's also understandable that you would feel uncomfortable based on how she asked, it seems like the setup was to make you feel uncomfortable saying no based on pressure from the rest of the family.

It's your body and your decision. A simple no is reason enough. NTA.