I found everything in this link made perfect sense and by following the principal rather than obeying every word was something that has worked for me.
https://lowcarbfreshwell.com/ However whether it would be suitable for you may depend on what medication, if any, you are taking.
How much help people get does seem a lottery but hopefully you will have picked up some good practice from your sister.
Would you like to share a bit about how you are managing your condition, what your HbA1C is and any medication as that will help people made appropriate comments.