Actually she luckily avoided a problem disconnecting the Tesla. I have a J1722 Charger at home (left over my Leaf and BMW i3). If you disconnect a J1722 charger from the Tesla you have to disconnect both the Tesla adaptor and the J1722 plug simultaneously. If you don't the Tesla system sends a fault code and the charger port locks and turns red (ask me how I know). The result is that you have to open the trunk and release the adaptor using the emergency disconnect cord attached to the inside of the charging port. If you don't disconnect it with the emergency release it will stay locked and you'll be unable to charge the car. I'm not sure how she disconnected it without causing the problem, but it was likely just the way she did it that didn't trigger the autolock and red light for an electrical fault. I've learned the hard way - if you're using the J1722 adaptor, click the disconnect icon on your phone, or better yet, on the charging screen. Wait for the light to turn white in the charge port, then hold onto the adaptor and remove it still connected to the J1722 plug in one smooth motion. That will prevent any error codes.
I believe I know why this is happening. Last week, at my work, using the J1772 adapter, I had the charge port go red.
However, what happened (this was a new Chargepoint station): I did not wait long enough after pressing the J-1772 latch release down, or did not press it down fully. This results in the charging cable not de-energizing before the disconnect - so it's like unplugging a vacuum or other inductive load while running. Since it was dark, I was able to see a 3-4 inch long electrical arc from the J-1772 to the Tesla charge port (due to inductance of course), as I pulled the J-1772 connector out of my Tesla. Whereupon the charge port went red, and I had to use the manual release for the adapter. And then fiddled around a bit to reset the error.
So, I believe the remedy is to push down that release fully and firmly, and give a moment before removing the J-1772 plug. This
should add 330 ohms in the Proximity Pilot connection and let the Tesla know to de-energize.
I haven't tried this many times yet so not sure whether it will be a "solution". The advantage of doing this is that you don't have to get your phone out - when you remove the J-1772, it unlocks the charge port adapter as well. I think with the simultaneous method you have to make sure it's unlocked first.
It sounds like there may be variation in the implementation, though, so YMMV:
From Wikipedia:
"Proximity Pilot: The Proximity pin, PP (also known as
plug present), as shown in the SAE J1772 example pinout, describes the switch, S3, as being mechanically linked to the connector latch release actuator. During charging, the EVSE side connects the PP-PE loop via S3 and a 150 Ω R6; when opening the release actuator a 330 Ω R7 is added in the PP-PE loop on the EVSE side which gives a voltage shift on the line to allow the electric vehicle to initiate a controlled shut off prior to actual disconnection of the charge power pins. However many low power adapter cables do not offer that locking actuator state detection on the PP pin."
EDIT: A spark that length I think means at least a couple hundred thousand volts! It was damp and it wasn't sustained (was more red/orange than blue). Guess there is a lot of inductance and/or the dI/dt was large!