My sister is 41 years old and in really good shape. She watches what she eats carefully (she is allergic to almost everything delicious) and works out on a regular basis, however she seems to be struggling to keep the little belly fat that develops below the bellybutton on women referred to as a foompah. It is small but it is getting harder to keep that tight mid section she has always maintained. She does tae-bo and works out on the total gym and recently started using the p90x ab ripper exercise to strengthen her core as well as her abs. any suggestions on what she can do to keep her tight abs tight?

As women get older they often have to step up their routines a notch to maintain your condition... which is sounds like she is doing. Changes in diet can sometimes play a role as well as the body will start to metabolize foods a bit differently.
The weights and resistance training can help maintain her muscle and bone density which also starts to become an issue in the 40's.
After sometime on the p90x, it will be interesting to see what results she sees. Keep us posted!