I thought a nice way to represent the bond between you as sisters, besides the obvious pinkies interlocking, would be a heart. It is not as cliché as seeing pinkies tied to the name, but still implies closeness, love, etc. Plus, it is a bold, clean shape that would still be recognizable at small-scales (such as on book spines, covers, business cards, etc.) And the heart is echoed in the publisher title (American Typewriter font), by using the same heart shape for the dot of the "i" in "Pinky" that is used as the main heart "PS" logo.
Also, keeping the publishing logo as not food-specific will leave the door open to publishing other types of books in the future, rather than having the publisher logo only tie to food/cooking.
Let me know if you would like to see any different color variations of any of my entries, and I will provide them for you.
Thanks for your consideration.
-Jake