Welcome to the forum
@feelinghelpless
Sorry to hear that your sister is struggling with severe hypos overnight. Severe Hypoglycaemia is defined as a low blood glucose event where the person with diabetes is unable to treat themselves and recover, and need third party help to get their blood glucose levels into a safe space.
SH becomes 6x more likely if a person had impaired awareness of hypoglycaemia, so that warning signs they would have relied upon to treat their low BG early. And impaired awareness of hypoglycaemia becomes more likely with more years lived with T1, and more exposure to low-level hypos.
It must be a very worrying situation for you.

Especially being so far away.
The good news is that there are some practical things your sister can do to try to reduce her chances of these severe hypos.
Additionally, there are tech options to help her and her boyfriend.
Is she on an insulin pump or injections? If on injections there are newer basal insulins which have less of a ‘peak’ of action. Overnight hypos can be caused by too much basal insulin, so getting her basal ‘right’ (as right as it can be at the moment, then tweaked on an ongoing basis) could help her enormously.
If she is on an insulin pump, there are options where a continuous glucose sensor can automatically suspend insulin delivery if levels are dropping too low - particularly helpful overnight when you are sleeping.
Some CGM (continuous glucose monitor) options also have options where the information can be shared ‘in the cloud’ and her boyfriend could be able to see what her levels were wherever he was to ensure she was safe, and receive alerts if her levels dropped into hypos.
Do you know if your sister uses CGM?