Glucose tablets have high glycemic index and a much faster absorbtion rate than say coke or digestive biscuits, so it really depends on severity of hypo, uptake etc. Its why some patients will respond to glucose and some require something like buccal Hypostop. Its not for the layperson to advise.
You mum should seek the advice of her diabetic nurse or speak to her leader with regard to diabetes.
My mums also a type 1 diabetic, and I wouldnt dream of tampering with her meds. By that I mean altering or tailoring her regime as the consequences would or could be much more than I could handle.
Good luck, and again speak to diabetic nurse fr alternatives and SW counsellor about syns, although I think they would say not to syn, and use as required.