Such a good question, @scooter8484. I'm afraid the answer may not be straight forward. Strictly speaking a do not resuscitate order (DNR) is a request not to have CPR if your heart stops or if you stop breathing. A DNR can be part of an advance directive. One's wishes regarding things like ventilation and feeding tubes can also be added to an advance directive. They are not specifically part of DNR. Sometimes people think DNR means "do not treat," but it doesn't.

Here's some information that might help explain further.
- Advance Directives and Do Not Resuscitate Orders https://familydoctor.org/advance-directives-and-do-not-resuscitate-orders/
- Deciding about Tube Feeding https://www.stjoes.ca/pdfs/PD3307_Deciding_Tube_Feeding(Internal).pdf

Is your grandma able to communicate at all? Is she able to take part in the decision to have a feeding tube or not?