This single-sided flat card simply say's "You'll be the death of me", printed in hand-set 14 pt metal Emerson type on a pre-war Chandler and Price Pilot table-top press. That's it. It doesn't fold or open, it's just an A6 (4.5" x 6.25") card with a single line of type surrounded by white space. You can use that space to write a note, or write something on the back. Better yet, don't write anything at all and let the sentiment speak volumes.
Whether this says "You'll be the death of me" in a cutesy winky way, or more sternly, depends on your intentions and the inference of the recipient. Note: envelope color may affect perception. A red envelope may read as a cute love note. A black envelope, something more sinister.