Sandra,
I know absolutely nothing about this product, but could I suggest that you ask your sisters diabetes clinic for advice on this matter. It may be that they can recommend the use of this, or may alternatively know of similar products that may be more suitable to your sisters needs. Also, if your sister is having frequent hypo's during the night, it will mean that her treatment may need adjustment to prevent/limit such episodes occuring regulary.
Regards
Nigel