Can’t tell if it’s common for people to ‘not’ have diabetes ?(my mum)

Long story short in April she suffered a ‘diabetic coma’ as her blood glucose was very high the past week leading to it. She had things like swollen feet and kidney problems, the swelling has subsided, the kidney problems also have subsided. She was being prescribed Metformin prior to this incident.

She’s been discharged and has been told that she isn’t diabetic and doesn’t need any meds. She is just on a renal diet for aiding her kidneys. Now my question is, to have suffered that ‘diabetic coma’ does it just mean that she wasn’t diabetic and just had hyperglycemia temporarily to cause it? I’m not too sure but all I know is the doctors have said ‘not diabetic’