Though looking scary, it may not be so serious.
Twisting of hands in your daughter case is called as tetany and is due to low calcium levels or dehydration.
As you have not mentioned regarding her consciousness, it unlikely convulsions or seizures.
Also you have not mentioned
the duration of diarrhea, but in main question there is mentioned chronic diarrhea
ie. Low calcium may present in chronic diarrhea along with deficiency of other nutrients. But in that case there may be other signs of malnutrition
like weight loss, low hemoglobin ie anemia.
So better to do stool Examination, complete blood counts, liver function test, kidney function test, blood levels of micronutrients, vitamin, ultrasonography
of abdomen may help in diagnosis.
Though some time anxiety with hyperventilation
(rapid shall respiration) may also cause tetany.
I hope with information provided by me, you will be satisfied.
Dr Abhay Mali