which types of diet pills will be beneficial for a women to burn her fat ?
Barring a nutrient deficiency that may be resolved via dietary supplements, stimulants are about the only effective pills for weight loss. However, everything that works better than caffeine is illegal (generally for valid reasons!). So, if coffee isn't helping you lose weight, it's unlikely that dropping 50$ on a bottle of magic pills is going to help you.
I'm afraid a healthy diet and exercise are the only effective, healthy, and sustainable means of losing weight for most people.
Lean meats, high-fiber whole grains, lots of fruits and vegetables, and of course keep the fats and refined sugars to a minimum. That means cutting junkfood, fastfood, and most restaurants out. They're in the business of selling food, and they succeed not based on how healthy their offerings are but on how good they taste. That means high fat, high sugar content.
If you eat this way and do nothing else you will almost certainly lose weight. But if you eat this way combined with regular cardiovascular exercise (5 days per week, 30-60 minutes is recommended as long as you don't have any medical conditions preventing you from doing so) you should shed fat rather quickly.
Some strength training is recommended as well, because muscle burns calories.
Those are the basics which I'm sure you already know. I'd start with that and keep an eye on forums like these for tips and encouragement from people who have been down the same road you're on. Remember: You can only fail if you choose to quit! This absolutely will work, but it requires you to work for it!