She prob would be in a diabetic coma. I'm a diabetic so not to scare u or anything she would know before she hit 0 it's easy to tell when a person is going low. Some sure signs of going low are:
-shaking
-hunger
-stuttering
Make sure she is not taking to much meds this happen a lot to my mom I also have diabetes
If get a zero she will go into a diabetic coma