It's probably worth noting that Sarah's hair is at its current normal length, which is longer than it should be due to a hair explosion.
Point being, Sarah isn't in a transformed state in this comic.
Anyway, the gist of this possibly confusing comic is that Susan is asking about the transformation watch Sarah is currently wearing, and Sarah is responding by insisting it doesn't do the things it most certainly does do and that she's telling the truth. As for what it does, consider why there would be an hourglass shape and dual watermelons.
No, it does not warp her through time and space to a watermelon patch. Fail.EDIT:
OH! I almost forgot to mention (meaning I forgot to mention it and then came back and edited this). Susan's poolside outfit is the result of a suggestion via Twitter
that she would wear a one piece swimsuit and boys swim trunks. I wasn't sure what she would wear (or if it would be even possible to get her poolside while still being in character), and it seemed like the logical choice.