I enjoy communication without words, and I think in a comic like this, the fun is sorting it out for one's self!
Okay, fine, I'll share authorial intent in case anyone wants confirmation.
Panel Three: Elliot asking if Ashley is going to shrink herself now.
Panel Four: Ashley considering staying normal sized or enjoying relatively giant cake.
Panel Five-Six: Elliot suggesting shrinking, enjoying cake, then growing to even larger than normal.