if you get her something, get something small. (if you are really daring you could get a body chocolate kit or something hahahaha!) My bachelorette party followed my bridal shower and so I only received gifts for the shower... not the party. Who is hosting the bachelorette party? If you can, ask the host whether you are expected to bring gifts. She should be able to tell you. If you REALLY don't want to call anyone up, get a gift that you can stick in your purse and you'll be covered either way! If no one brings gifts just save it and give it to her quietly after the party or when everyone is distracted. If people DO bring gifts... then act like you knew all along!
These things are often hard to tell unless you ask- just like some bachelorette parties have male strippers and beer and "man shaped" pasta, and others are very mild affairs where you drink a few mamosas and joke around.
Good Luck!
-M.