My Ex-mother In-law's Feet Are Deteriorating Badly, It Hurts Her

My ex-mother in-law's feet are deteriorating badly, It hurts her to try to walk and even putting her slippers on. She has diabetes and I don't believe she is taking her insulin like she is suppose to be. She will not get off of the couch to even exercise her feet. Is it true that she could lose her feet faster if she dose not exercise her feet to increase blood flow?