First, massive kudos to Jason Miller who correctly named the Shakespeare reference in the first Spike-Drusilla encounter. He got both parts of the answer. First, the red herring: Drusilla says she plants daisies, but everything she puts in the ground withers and dies. Although Joss Whedon is definitely drawing a parallel to Ophelia, it is not a direct quote from Hamlet. The specific Shakespeare quote I was referring to was Spike's line "I'll chop her into messes," which Othello says about Desdemona in Act 4, Scene 1 when he thinks she's being unfaithful to him. The full line is actually, "I'll chop her into messes, cuckold me!" Very different context from the Spike-Drusilla scene. Although, on second thought, it actually kind of resonates given the later love triangle between Spike, Buffy, and Drusilla. (Spike, of course, is the one who does the cuckolding to Dru.)
Now, for the next Buffy Thought of the Day. This one's also interactive: Name the Shakespeare reference in my Drusilla song (including the original quote). This one should be a cinch.