She goes back and forth between scenes wearing running shoes and hiking boots.
When Iris opens her driver side car door while the killer is talking to her, it is shown she can open it entirely enough to go into her car, but when the camera changes to showing the killer behind her or in any other angle, the driver side door can barely be opened at all.
All Paralytic drugs also inhibit breathing. So she would have to be on ventilator support to stay alive.
When they are at the gas station, it shows Richard filling up with gas on the passenger side of the truck. On those trucks the gas cap is on the drivers side.