It appears the round was a different size than the other, hence the woman did not shoot herself.
So who did shoot her? The other robots had lasers rifles, were we to ever infer what happened as far as her getting shot?
Yes, it's left open
But the only important thing to know is Mother was lying about the Woman having shot herself
I can believe the robots shot her in an effort to "herd" her into the vault
BTW, I'm not sure those were laser rifles - they seemed to have laser sights, but the rifles themselves could've still been projectile weapons
It was poorly produced because the bullet pulled from the wound was not the same one that was shown in the vial. The first one pulled from the woman was grey/silver appeared to be solid lead bullet... the one in the vial had a brass tint and appeared to be a jacketed bullet. Worse yet the bullet entry wound was much to large for a bullet of that size. In the end it didn't matter because mother was trying to cause the girl to belief that mother was being dishonest which was the point of the test.
shareI guess the filmmakers made the wound look bigger because they wanted it to be more dramatic. They needed the two bullets to have a size difference, but couldn't make the big bullet any bigger.
sharePerhaps she used a weaker gun with smaller bullets to shoot herself as she only wanted to be wounded and not too close to dying. The robot she wanted dead so she used a proper gun for that.
shareMaybe a robot with a different type of gun, just to justify the lie?
Btw, do we even know what kind of bullets the droid guns shoot?