All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
Such a method in enjoining what is good and forbidding what is evil is inappropriate to use towards mothers, and also giving advice to them in front of others, be it a parent or someone else.
You should choose the appropriate method, such as using the indirect approach of advising.
For example, showing her a video or an audio clip of medical specialists containing instructions for a diabetic person regarding his medication and diet. The same applies to wrong deeds that she may do, whether they are related to religion or worldly matters, benefiting from the specialists on the matter is the correct way.
Allah knows best.