Ight, im not a girl but I will still help ya out.
Doing crunches 50x a day wont do anything. Even 1000 crunches wont do anything. As an example, the record holder for doing the most ab crunches, you can see the rolls of fat on him.
All crunches do, is just make your stomach harder. Dont get me wrong crunches are very important to maintain stability in your workouts. And if you are already skinny (but dont really have abs) then crunches can help a lot there to make them pop.
To get good abs (and by the way a six pack on women is different than a six pack on guys. look wise). You gotta drink water, eat correctly, and workout. (A lot of routines on youtube for women that you can find). Workout meaning pushups. Also, play a sport, or go out for a jogg. You should increase your pace every minute then slow down every 2 minutes. It should last around 30 min with a warm up and a cool down. This will elevate the metabolism and its twice as effective than just jogging mindlessly.
Eating: This is the most important part. Replace white bread with whole grain and whole wheat. Dont eat a lot of sugar (6-8 grams a sitting). I would say consume around 70 to 100 carbs a day. Personally, I try not to eat that many carbs, only after my workout so my body absorbs them instead of storing them as fat.
There you go :)