My wife is not blind, but I have run this identical scenario with her in case I have a heart attack or stroke or something.
Step 1: Put the car into neutral. Since the engine is still running, brakes and electronics will still work. Both our cars have typical automatic gear shifts and will go into neutral by simply pushing it forward out of drive.
Step 2: Activate emergency brake. Both our cars have mechanical handbrakes which are able to be activated from the center console. Some cars have e-brakes which are to the other side of the driver and cannot be reached by a passenger.
Step 3: Activate hazard flashers. Both of our cars hazard flasher switches are on the dash, and are reachable by the passenger, but our older truck had the switch on top of the steering column.
Step 4: Call 911 and hope for the best.
All of these should be possible in the majority of vehicles for most people who are legally blind, as long as they know where the controls are located. On the Ridgeline both the hazard and the gearshift are in those locations, I am not sure where the e-brake is located, most likely the driver footwell left side, so the passenger would not have access.
I am unsure if drivers safety aids will still function in N, but that is easy to test yourself.
It would not be safe to attempt to put the car into park at high speed. Most likely the transmission would ignore that attempt for safety reasons, but if it did lock the park pawl it could cause an uncontrolled spin of the vehicle.
Edit to address comments on e-brake
Most cars on the road have an emergency brake that connects a cable to a drum brake on the rear axle, and some have an electronic "park brake" that is not an emergency brake.
For cars with a typical "hand brake" type emergency brake, these apply increasing brake force the harder they are pulled. A locking ratchet will keep the brake at that position until it is released. In my car, 1 click on the ratchet will not actually apply the brakes due to the free travel of the cable and mechanism, but it will turn on the brake lights. This is important because drivers behind you will have a visual cue as to your intentions before they can see the car is slowing down. Additional clicks on the ratchet provide increasing levels of brake force to the rear axle only, and allow safe and stable deceleration once you reach the correct click.
One of the reasons why hazard flashers is the 3rd step after neutral and brake, it that it is much faster to blindly slow the car down than it is to find the hazard flasher, a small button which may be flush with the dash. The time it takes to find the button, then slow down the car, may allow over 1000 feet of additional travel, potentially towards stopped or cross traffic.
For cars with electronic park brakes, some of them may work in an emergency. I think I tried that on a Mazda SUV, and it provided adequate brake force to slow the car down in a safe and stable manner. However not all cars may respond this way, you should be aware of how yours does ideally during a safe test drive at a dealer.