Worked with a lady whose 20 something year old daughter went to Mexico on her honeymoon. Within 48 hours of returning, she was #1 on the list for a liver transplant. Never did hear what happened but she got into something that essentially killer her liver. Her husband was fine.
I would suspect poison mushrooms. They will kill your liver quickly, or perhaps the Covid shot. Many drugs can be toxic to your liver if one is sensitive to a particular drug. Tylenol in excess will also take your liver out every time without immediate treatment.
It would be interesting to know what she ate, drank, and any meds she was on. Lastly it could be foul play.