When you call rental offices, ask for a power chair with 'Attendant Control'. I know Jazzy makes this an option and I suspect a rental agent somewhere has one.
What would be better but less likely to find is a manual chair with attendant controlled or adaptive power assist. Adaptive power assist registers input from the wheels or indirectly from the handles on the back of the chair and applies energy to the motors only under that condition. So there's no runaway situation and it essentially controls like an unpowered chair. I've played with a couple of these setups and it honestly feels like pushing an empty chair around even with a 230 pound guy in the seat.
I tend to agree, and yet if we're talking about control by someone of ... dang, how to put it... ok, someone who's generally sharp when it comes to spatial reasoning, then I think most people get the hang of it pretty quickly. If the OP can navigate a shopping cart through a crowded store she can likely figure out a wheelchair. And it really depends on the particulars of the mobility tech.
For instance, I don't like the SmartDrive system for something like this because it has the ability to run away. Any system that doesn't require direct input has that risk. Imagine an
ECV where the throttle stayed locked in the on position and required you to push a different control to release it.
On the plus side, there is some amazing tech coming down the pike for people who can afford it. I was politely shot down by Whil when I requested developer access. They were super cool about it but the projects I would like to integrate into their platform are things they are already working on and the last thing they need is someone like coming back claiming they took my IP. By 2030, self driving power chairs will be commonplace. For people with $60k to spend on a chair anyway.