I mean, just think about the staging possibilities for this. like she falls to the ground and Hamlet goes “How does the queen?” so he is noticing somethings wrong. he’s concerned. does he stop fighting then? does he drop his rapier when he sees her lying there? does he run to her as Claudius tries to wave off what’s happened, when he says “she swoons to see them bleed” ? is Hamlet holding his mother, trying to help her up as she’s muttering, “No, no, the drink, the drink!” Hamlet’s confused, trying to help her up but she’s not trying at all, she’s just trying to get her son to look at her, she’s grabbing his hand, squeezes it, and he realizes something is really wrong, why isn’t she trying to get up? maybe she reaches up, touches his cheek, remembers when he was just a toddler, remembers when things were better, remembers before all this happened when they really were much closer, remembers what he was saying after the play and how much hamlet just misses his dad, she caresses his face and wishes she had more time. that’s when she delivers the line. that’s when she says looks at her son and murmurs “O my dear Hamlet.” because there’s nothing else she can say. then she looks at claudius, then the goblet lying on the floor with the poison spilled out of it. “the drink, the drink.” she looks at her son and she can barely speak but now he realizes, now he understands, or at least she hopes. “I am poisoned,” she whispers, and if she had more time maybe she would say something else. but she has no choice. that’s the last thing she says, because the last thing she does is try to save her son.