How did the girl who drank the most survive?

Two girls ate dinner together.
They both ordered iced tea.

One girl drank them very fast and had finished five in the time it took the other to drink just one.

The girl who drank one died while the other survived.
All of the drinks were poisoned.

I will be doing these murder mystery riddles which there are 11 in total.
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Also the first one is called, "Iced Tea."
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I'll give the answer once this question has been up for 1 day.
How did the girl who drank the most survive?
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