seems (I know I know it’s a movie) utterly impossible. She at first came to fight with thanos. She wasn’t a resident of earth. Tony never saw her. Tony seemed to of snapped all the people with thanos away. How would tony think “snapneveryone away except gamora who I didn’t know was here” Like really. Did tony leave other members if thanos’ armybehind? If so he sucked and deserved to die I’m high as ****
Considering Tony Stark is smarter than all of us, I'm sure it was that simple. And if you saw Infinity War, you'd know his minions were very devoted to him... to the point of treating him as a deity. The foot soldiers are devoted to him like your dog would be to you. So yeah, it would be that simple.