OK let's take a step back and breathe....
Your car is damaged.
It is an inconvenience.
The MD was wrong to drive away.
No one was injured. No one was killed.
I would be very careful about playing the "pregnancy/stress/I'm calling out sick" game. That can backfire on you. You don't want people to start thinking you are unstable because of your pregnancy.
You have notified the police, your insurance company and your HR Dept. Let them do their jobs.
If the car rented for you is not acceptable, call whomever you rented the car through (your insurance vs. her insurance) and tell hem that the car is not acceptable because you cannot get in & out of it easily and you'd like a car that's more suitable to your physical needs at the moment.
If the MD approaches you again, simply say to her " I do not wish to discuss this with you and do not want you to try and speak to me again". Make it a very clear statement so that if she tries again AFTER that, then you can start with the harrassment stuff.
Be aware that the MD probably won't get fired, despite what the HR policy says. I assume you work a a hospital, there is a double standard where MDs are concerned and you have to decide how much energy you want to expend on this situation. Sure, if you make enough noise you can probably get her fired. But be VERY aware that YOU will then also be branded a troublemaker and they will be looking for ways to get rid of you.
At the most, if someone contacts you from HR, my statement to them would be "You have written policies in place which guide you as to what should be done in his situation. I assume you will do the right thing and follow YOUR policies".
As far as contacting a lawyer...well, you can certainly do that if it would make you feel better and perhaps the lawyer can give you some guidance on how this thing will probably shake out. But I wouldn't start sic-ing lawyers on anyone unless you need to. Don't tip your hand unless it becomes necessary.
Is the MD harassing you? Well probably not yet. One encounter where she was somewhat desperate to reserve her reputation does not necessarily denote harrassment. If she coninues to approach you, you have more of a case. Just make it quite clear that you DO NOT want to speak to her, period.
Again OP, determine how much of your time, energy and angst this is worth...
It's a car accident, not a cancer diagnosis. Keep your perspective.