Hi
@JJ34 and welcome
The answer to your question very much depends on a) which type of diabetes your flatmate has been diagnosed with and b) what medication they have been prescribed.
From what you say it sounds like type2, but it would be helpful for that to be confirmed.
If they have been prescribed any blood glucose lowering medication (i.e anything other than metformin) then they should also have been given a blood glucose meter and testing strips so that they can monitor whether their levels are either dropping low or going too high. She should also have the Patient Information Leaflet from the medication package which will explain the possible side effects and what to do.
If it is metformin then the likelihood of her going too low is practically zero.