Tinsyl, your response (avoiding beans completely) is totally understandable...but I would say, from my experience with a dad who has Type 2 and a toddler with Type 1 Diabetes, that it's futile to try to micromanage someone else's diet, especially if they are not a child. In my dad's case, for instance, he routinely eats what he wants no matter how much my mom tries to control things. Does your mom have any friends? Does she ever eat in a restaurant? Does she get invited to other people's houses? In all those instances, she will want to eat what others eat, and she will resent you telling her no!
It's better to do the (hard, time-consuming, scary) work of figuring out how to dose insulin for the foods she does want. The ones that are horrible for BG she can eat in special situations or in moderation. I'm of the firm belief that there is a way to bolus for almost any food, as long as it's not spiking BG too fast, there should be a way to cover it with insulin. The trick is figuring out the crazy dosing regimen.
Personally, I would keep a food log. As the column headers, write out the time, the BG reading, the dose of insulin, the food, the grams of carbs. Then just track how the BG changes over the course of 4-8 hours in response to that food, and record any additional insulin you give. I'd test BG every hour after one of these mystery foods.
Keep changing the dosing schedule based on what you see. Is she going low after beans before going high? Experiment with delivering the insulin after her meal. Is she going high for hours and hours? Up the upfront bolus, add up the total amount of insulin you gave her over a 4-8 hour period and then try to administer some of that insulin upfront or soon after her meal. If she's high for 4-6 hours, I'd experiment with bolusing upfront, then again at 1-hours, 2-hours, 3-hours.
We've been doing this for weeks on pancakes. We go to the same restaurant each Saturday, my son eats basically the same meal, and we try different boluses. We are getting progressively closer to the perfect pancake bolus. Pancakes aren't great food for anyone, but it's not fair that my two-year-old has to completely eliminate them just because we couldn't figure out how to bolus for them.
I'd also figure out how to subtract the insulin on board for your mom and administer correction doses or additional insulin earlier than 3 hours after her last dose. Humalog has a DIA of 5-6 hours, and about 20 percent of it is active each hour. There are IOB calculators online to help, but you can roughly assume that 80 percent of the insulin you gave is still active after an hour, 60 percent after 2 hours, 40 percent after 3 hours and so forth. It really is HUGE to be able to proactively prevent a high rather than retroactively chasing one with more insulin.
Finally, hypoglycemia of 50 is not great, but not necessarily dangerous. Most of us non-diabetics spend at least half our time between 60 and 100. I wore my son's almost expired transmitter a while back and it was eye-opening. I spent most of my time between 70-80 -- which is considered hypoglycemic for my son. I dipped briefly down to 59 on my own once, and only then started feeling shaky. When I was in the mid-60s I felt vaguely not great but certainly not overtly hypoglycemic. I would be less scared of hypoglycemia between 50 and 65 when your mom is not sleeping and know that the procedures in place, such as checking blood sugar and treating with fast-acting carbs, will work to get her back up.
Everyone on here is right that certain foods do spike blood sugar much more than others with the same carb count for some people. Ultimately, you will find if you test your mom an hour after eating that many, many foods are sending her high post-meal, not just the ones you see raising her BG 2 or 3 hours later. You can't eliminate all of them, so if you have the mental energy, I really would try cracking the code to individual foods she really loves. At least that way you won't be so stressed out when she does wind up eating them.
You will figure these things out for your mom! But also remember to take it easy: you have years to figure this stuff out, and you should pace yourself. Being a caregiver is exhausting and you need the emotional reserves to be a good daughter and caregiver to your mom.
Be okay with letting someone else do the care sometimes -- even if it means her BGs aren't perfect.