N.T.
My three year old and two year old boys BOTH pretend to get injured for the attention. An example: Kid #1 bumps the elbow and crys for the "boo boo pack" (Ice pack) kid #2 runs up holding HIS elbow and wants the boo boo pack from kid #1 even though he doesn't have a "real" boo boo. I also catch them independantly faking injury when they think we're not looking...probably because they know that an injury means getting scooped up, cuddled, and basically pampered with one-on-one time (hard to find with two toddlers!). And they are QUITE convincing! I wouldn't know it was an act if I didn't catch them once in a while.
Do everything you can to make sure there isn't a health problem, but maybe also try starting some special moments to emphasise healthiness so the special attention she gets when she has a tummy ache is focused differently? Like have a little dance and a special song or something when her tummy STOPS hurting? If the tummy aches start getting shorter in duration (so she can get to the song faster), it'll be very telling :) Good luck!