Seems like a lot of contributing factors:

• The private ranch seems remote and has tough terrain, which impeded rescue response, delay and limited resources
• The fact the Model X "shifter" is touch screen based and Tesla has an 'auto-decide reverse or forward' feature might have contributed to her confusion
• It is likely the electronics disengaged, making the exterior door handles unworkable, so the only door handles that could have worked would have been the manual release inside
• She might have panicked and forgot or did not know about the manual release, since the usual way is to press a button, because buttons are... cool I guess?
• She might have done the manual release but it failed to open because of the weight of the water. Once water got in she might have not thought to try again, or she was somehow incapacitated at this point
• The glass was evidently not easy to break. The rescuers tried and failed.
• Tow truck driver was afraid of the electricity

The people on premise seemed to try, but given that even with trained rescuers with equipment they failed to extract her, I can't say they did "jack shit", there's probably nothing the people on premise could do, except maybe tell her to let some water in quicker to open the door at the right time.

So:

• As you say, even if on private property, don't drive impaired (although it's not stated whether she was drinking or not)
• Beware that a remote property might be great for showing off you have a lot of land, might not be so great if you ever need help, it will take a while and be of lower quality
• Tesla's "button and emergency release as wholly independent controls" is a bad idea
• Tesla's "touch to override, but otherwise let the car decide if you want to go forward or backward" is a bad idea
• Drivers should be reminded about how to open the door if water is outside (try to let enough in to open, before you get too deep).