Ophelia, following Hamlet's exit after he has insulted her greviously, is incredibly upset by what she has witnessed. What is interesting however is that she is not upset by what Hamlet said to her so much as the way that his actions indicate how he is mad and how this madness has impacted his character. To have known Hamlet when he was sane and healthy and then to see him in this condition is something that Ophelia finds very difficult to see, as her speech makes clear:
And I, of ladies most deject and wretched,
That sucked the honey of his music vows,
Now see that noble and most sovereign reason,
Like sweet bells jangled out of tune and harsh;
That unmatched form and feature of blown youth
Blasted with ecstasy.
Ophelia is therefore very upset by Hamlet's actions and finds it very hard to have witnessed such behaviour in a man that she loved and whose character she admired so greatly when he was well and healthy. She therefore finds what she has witnessed very difficult to cope with. Her love for Hamlet is clear; now she has witnessed the man she loves exhibiting madness. Thus Hamlet's "noble mind" is "o'erthrown," in Ophelia's estimation.