That sounds like very strange advice, like contrary to all standard diabetic management advice. Do you think you might have misunderstood them. Usually the advice is if you're in the 4s to go to sleep have some slow acting carbs to see you through the night.
Your body doesn't produce glucose, it stores glucose from what you eat. It stores glucose in your muscles - that's why people running marathons eat this glucose gels half way round, because they've used up the glucose in their muscles and they're replacing it. It also store glucose in your liver.
In your pancreas there are two kinds of cells to know about. The first is the beta cells, they make insulin and, as you have type 1 diabetes, they are the cells being killed off by your immune system. The second is your alpha cells, when you get low blood sugar the alpha cells release a hormone called glucagon, this is a signal to your liver to release the glucose it has stored and raise your blood sugar. In a newly diagnosed type 1 alpha cells should be functioning in tip top form, but the alpha cells are vulnerable to getting worn out in a type 1 diabetic. It is not wise to rely on alpha cell action to solve your hypos - that would be thinking I'm in the 4s but I'm ok to go to bed without eating anything because my body will still have sugar in it because to get at the sugar your body's got to go through quite a complex hormonal process that might make you feel a bit unwell and could be easily avoided by eating some carbs before bed.
Maybe the advice not to have slow carbs when in the 4s was to have fast carbs in preference? As obviously, fast carbs will get you to a good number to go to bed on quicker.
If your dropping overnight that does suggest your basal dose is too high. The job of your basal insulin is to keep blood sugar flat when you aren't eating (to bump it up) or bolusing (to knock it down). So, in an ideal world, you should wake up at about the same number you go to bed at with a nice flat line overnight. You can do some overnight basal testing to see if your basal dose is working for you -
https://mysugr.com/basal-rate-testing/
You might also want to look into the freestyle libre, which would show you what your overnight blood sugars looked like, or a CGM, which would alarm if your blood sugar dropped under a certain level. These would have to be self funded, but might allow mum a bit more sleep.