"She only drinks hot water."
In English the word 'only' modifies the term 'hot water' so it ought be places right next to that term. If it is placed as the answer places it in Chinese, it means that she drinks it as opposed to doing sth else with the water. Is there a rule which demands that this adverb must be place in Chinese where it is placed?
Well yes, but actually no.
The trouble with English grammar is that a lot of it was written down a long time ago. Some of these rules are still valid. In other cases, the language has moved on. In still more, the rule applied in the prestige dialect of those writing it down, but actually was never followed by the majority of speakers. And in some, the rule was literally made up to set a preferred style for something that no-one previously had a consensus on.
What you're saying here makes logical sense, but as a native speaker of modern British English putting 'only' anywhere but before the verb feels a bit unnatural and stilted, and I believe most Americans would agree.
Yes, this technically causes ambiguity, but in practice - like 会 for both 'will' and 'can' - context makes the meaning clear.