Alcoholics often develop peripheral neuropathy because of the nutritional deficiencies caused by not eating correctly while they are drinking. You are off to a good start with the vitamins. B1 , B12, and D3. Make sure the D you are using is D3 and the B12 you are using is methylcobalamin. These are the usable forms of the vitamins for your body. A good multl B vitamin and a good multi vitamin would be a good idea. It's important that she eats a balanced nutritious diet.

Since she may also have diabetes, she should be given an A1c Test which indicates the average blood sugar level over a 3 month period. This would help to diagnose whether she is a diabetic or not. Repeat the test 3 months later after she has been taking the vitamins and eating well for that period. I wouldnt jump to conclusions based on that first test since she has just started to take action to turn things around. Its possible that a combination of dietary deficiencies and diabetes has caused her peripheral neuropathy

The good news is that peripheral neuropathy caused by alcoholism/ dietary deficiencies is one of the few causes of peripheral neuropathy that can get better long term.