Yes, VW assembles the pack, but Samsung SDI makes the individual prismatic cells. The 35.8 kWh e-Golf battery pack is created in a 88s3p (s=series, p= parallel) configuration, and contains a total of, you guessed it, 88x3=264 cells. At a nominal cell voltage of 3.67 V, the pack voltage is 88 cells *3.67V per cell=323 Volts at the pack level. All of the electronics in the car for charging, powering the motor, HVAC, etc. is built around the cell voltage varying from about ~3 volts at the low end (~264 Volts at pack level) to about ~4.1 volts at the high end (~361 Volts). If one cell in the group of 88 cells wired in SERIES becomes disconnected or has a major issue such as an internal short, BMS will attempt to prevent a fire and shut the whole system down. If a cell became disconnected, the voltage would drop to 0 for that single group of 88 cells in series. It is not as simple as the BMS deciding to "isolate" a cell - the system can not work in that fashion as it is designed. There is no way to isolate a single cell because they are all interconnected in series within each group of 88 cells. Since it looks like the "battery cell defective" code means one cell is dead, the car must be shut down or your wife's car may have become very toasty.
I wish you the best of luck in getting this figured out. VW will probably need to remove the battery pack and replace the faulty cell or repair the connection (depending on the true problem). How are you able to reject the car and get all your money back if this is not a lemon law issue?
2017 e-Golf LE, Multi Coat White with Black Vegan Leather interior, purchased in early 2018
2015 e-Golf SEL leased for three years, returned in early 2018