
Quoting
LawResearcherMissy
MIL, who was an RN for 40 years, tells me that if she had pulled a stunt like that, she would have lost her license - regardless of who she pulled that stunt on.
Unless she had explicit permission from the child's parents, it's irrelevant what capacity she was performing it in. You don't perform medical tests on anyone - not even your minor grandchild - without the patient's permission, or in the case of minors, without explicit consent from their parent or legal guardian.
Grammy needs her ass kicked up over her head and a complaint filed with her nursing board.