Abs are one of the hardest muscle groups to develop on a woman, namely because it is usually the problem area that each woman has when it comes to storing fat. I have other problem areas, namely my legs and butt, that are the last to lose body fat from so my abdominals are definitely watch catches people's eyes! Fat is stored in a predetermined fashion and many people are under the assumption that exercises that target muscle groups will also burn fat from that area. Unfortunately, this is not the case. Therefore, you have to have both good nutrition accompanied by regular exercise incorporating weights and cardio to ensure continued progress.
One of the most overlooked aspects with weight loss is nutrition and the fact that you can do a lot without a gym membership (home based exercises) and even minimal exercise in general. Weight loss is 80% nutrition, 20% exercise and 110% commitment. Weight loss should not be looked at as a lose weight quick approach as there are some extreme diets out there that yes, will achieve the results of losing weight quick, but not in a healthy or manageable way so the chances of having a bad rebound after the dieting period is extremely high.