The best thing for your mother to do would be to discuss her dietary habits with her primary care doctor
, who can help her determine if they are appropriate and sustainable, or if she might need to make some changes to her regimen.
Protein in and of itself is not dangerous for most health people, with the exception of those who have chronic medical conditions which limit their body's ability to break down and handle protein. For example, those who have chronic liver disease often need to limit the amount of protein they ingest.
What is more of a problem for otherwise healthy people who ingest large amounts of protein is that they may simultaneously be avoiding other types of foods. For example, many people on protein rich diets avoid carbohydrates. This can lead to ketosis, or excess breakdown of fats and proteins in the absence of a good source of carbohydrates, which can be counterproductive to an overall healthy lifestyle. Also, in those with kidney problems or diabetes, ketosis may be dangerous.
Finally, those with restricted diets of any sort may be at risk of developing a nutritional deficiency or a vitamin deficiency due to not ingesting a diverse diet.
Again, I recommend that your mother discuss this issue with her primary care doctor.