Hi,
If she is having insulin twice a day it is almost certainly what is called a biphasic insulin. This contains some longer and some shorter acting insulin. These insulins have a peak of activity ie when they're at maximum strength, it is important to eat regular meals to coincide with these peaks and sometimes small carby snacks may be necessary to avoid hypos. You really need to discuss the best times to eat and particulary find out if a snack may be needed before bedtime
A blanket cut the carbs idea may not be ideal for her, we don't know what she was eating before. I know if my elderly mother cut her carb intake she would be eating very little indeed. Regularity of meals and the type of carbs eaten though are (in my opinion) both important.
One way of looking at a meal is t the Idaho 'diabetes' plate, the size of plate might be smaller than the one suggested
http://www.extension.uidaho.edu/diabetesplate/who.html
It is better to choose lower glycaemic index carbs (from starches, fruit and veg) as these should cause lower spikes than higher gi carbs. For example it is better to choose a few small new potatoes than a jacket one or mashed potato, it is better to use a low GI bread like Burgen or a grainy bread rather than white or wholemeal. Some varieites of rice are very hig gi whereas basamati is much lower (and any rice overcooked will be quite high gi) There are lots of general lists on the net but the best source of info about the GI is this one.
http://www.glycemicindex.com/
The FAQs are a good explanation, the newsletter is a good source of tips and recipes.
Testing before , 2 hours after meals at bedtime and even during the night will help show whats going on so you can see the patterns and her insulin/food adjusted accordingly.
I hope that you've been told how to deal with low blood glucose ( conventional advice is to take 15g of fast carbs ie dextrose or lucozade, wait 15 min test again; if back to above 4mmol take a 15g snack of longer acting carbs, if still below 15mmol repeat the dextrose/lucozade)
Its quite a challenge to deal with this at 90, I have heard of one person being diagnosed with T1 at 90 before but it is very unusual. I really hope that you have some good support from the doctor and nurses.
