Definitely avoid ALA unless your friend can tolerate it in very low-frequent dosing (cutler protocol).
Vitamin C in large does is a must. Start reading about sodium ascorbate. Also read up on sodium ascorbate enema. If your friend can get IV vitamin C, do it.
Home made liposomal c with food ingredients.
Search for the instructions on livingherbalfarmacy web site.
Two natural chelators that will not make you worse are modified citrus pectin and micronized liquid zeolite.
Your friend probably also has high copper. I wish I had known about copper when my mercury issues were really bad. Copper toxicity has many of the same symptoms as mercury poisoning. Try taking zinc carnosine and avoid high copper foods. By the way, vitamin C helps detoxify mercury and excess copper.
coffee enemas help with copper issues, but mercury sensitivity complicates things. Try a coffee enema a couple of times a week, provided you are also taking modified citrus pectin, and/or zeolite in case mercury gets mobilized by the coffee enema.
You could also try reduced glutathione, a form of glutathione with all of the co-factors for proper absorption. I’m not sure reduced glutathione is helping, me but it is not hurting.