JustAGirl,
Please excuse some of my American cousins. They seem to think there's no other country outside of the United States. (They use a different measuring system when it comes to measuring blood glucose levels there. Your mom's 2.5 mmol/l (millimols per litre) would measure 45 mg/dL (milligrams per deciLiter ... note they also spell litre different to us in the civilised world ... or should that be civilized for my American cousins? lol) over there.
As you say, 2.5 mmol/l is very low, and your mom was in danger of losing consciousness. It's imperative that you get some quick-acting glucose into her at that stage, and I'm sure you did that.
I'm quite convinced that if you did approach your mom's doctor for a review of her medication, s/he will say that it's because your mother hadn't eaten, or had undertaken strenuous exercise. After all, a doctor can never be wrong, can they?
My suggestion is that your mom should be testing her blood sugar levels more frequently ... at least until such time as her medication has been reviewed.
To put your mind at rest a little, I've had a blood sugar level of 1.7 mmol/l (31 mg/dL) today, and realised at just the last few seconds before I was incapable of doing anything for myself. Luckily for me, I don't live alone, and we keep glucagon injections in our fridge, but there was no need for them today. I was able to get some glucose powder mixed up into some water and drink it before lying down and waiting for recovery to happen.
I'm quite convinced that your training will teach you that it's not always the 'lowness' of the blood sugar level, but how quickly it drops to that level that causes people to lose consciousness.
I don't know if you're from the UK, but there seems, of late, to be some doctors not wishing to prescribe many blood testing strips to type 2 diabetics, which your mother must be if she's only taking pills/tablets for it. Speak with your doctor about this episode and request more testing strips. If s/he refuses, ask to be referred to see an endocrinologist/diabetologist, and a dietitian. I'm quite sure you'd get more co-operation from them than you seem to be getting right now.
Edit:
Please believe me people, that's not me giving the thumbs down.