No quote to spoil the fun, see above.
You’re worrying unnecessarily.
The fatalities are associated with people who have liver or kidney problems, not normally healthy adults, and the fatal level described is likely a result of overdose.
Your sister is taking about one third of the dosage that would be normal for her body weight. Aparently the doctor has chosen to give the smallest dosage that will be effective, and will of course verify this with a blood test.
Reading medical test info may make the confusion worse, since if you don’t know how to interpret the results, or only see the parts about deaths and other possible bad side effects, you miss the actual amount of risk, which may be very low.
Anyway, here ya’ go, have fun.
ps. I’m not a doctor, but did take this for six months, at three times her doseage, and the same body weight, and suffered no side effects whatever. Your mileage may vary, of course.