Hello Mario, I am sorry that your mother has ALS. But you are in the right place for quality information and support from our members. And thank you for your question.
Regarding chelation therapy, it has not been recommended for treatment of ALS. I have provided a link below for you to an article written by Dr. Bedlack, neurologist specializing in ALS. This article addresses a number of complementary/alternative therapies, you’ll find chelation therapy on page 14.
Bottom line: heavy metals have not been found to cause ALS. Treatments to “remove” heavy metals do not cure ALS.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4712627/