When this strip appeared Ophelia's last line was originally, "to let thou knowest that I would be thine."

But mandareevz immediately pointed out that "thou knowest" is the inappropriate nominative case, and should be "thee know", in the accusative case. Unfortunately, this would remove a syllable and throw off the iambic pentameter.

So he kindly came up with the alternate line that you now see, which is, I am assured by people more fluent in archaic English than myself, grammatically correct.