Hungry all day and not eating dinner. Does anyone else deal with this and how do you handle it?

My mother in law forgets when she last ate. She eats breakfast pretty late (10:00am) and then usually has a snack mid day (crackers or potato chips). Between breakfast and dinner she is constantly asking when is dinner and says she is hungry. When dinner comes (around 6-6:30) she tends to eat less than half her food (if that) and says she is full. This happens whether she has a snack during the day or not. The problem with it is she is diabetic. I have asked her Dr to change her insulin to a sliding scale and she refuses saying she doesn't do sliding scales for her patients and proceeds to tell my MIL to eat her food. (Yeah well that's not going to happen). She says she needs the insulin. So we give her the insulin and then she goes low and we have to pump all kinds of stuff in her to get her sugar levels back up. Yesterday she dropped to 59. My husband and I disagree on how to handle this so since it is his mom I let him choose and that is why she had her insulin last night, she got mad and a left the table after eating a piece of bread and a bite of potatoes. 4 hours later her BS is 59. Sorry, that was a bit long of a story. My basic question is does anyone else deal with this and how do you handle it? I have my own opinion (I am a registered nurse) and my husband (no medical background) disagrees with me. If you deal with this sort of situation, what do you do? I will also tell you that I asked him the other day if he wanted her to have insulin and he said yes, she sees biscuits on the table so she will eat. She did not eat enough went low that day as well.

Thoughts?