she was too slim two years back but suddenly she started eating a lot and did notgive attention to her increasing weight.
now she wants to loss her weight but she says she tried many things she feels dizzy and fainted that she could fall because of weakness
any remedy or any experience or any handsome advice.

She might think about trying this book called "The Movie Star Diet" by Steve Simmons. It helped me lose thirty pounds in 2 1/2 months when I didn't think anything would work. My goal to begin with was only 20 lbs! It has a really easy plan to follow and an excellent workout as well.

You can't target weightloss to one part of the body, but she can start doing a lot of cardio and weight lifting. If she's fainting because of weakess, she's either quite sick or not eating enough. She needs to make sure she has a balanced, heathly diet full of fresh fuits, veggies, whole grains, lean meats, and not too much other stuff.
Tell her to do cardio at least 3 times a week (6 if she's motivated) for at least 30 min per day. Start her on a weight training regemine of chest and arms one day, legs and butt the next, and abs and back the next, and start over. Make sure she's not starving herself though. That's counterproductive in the long run. Or you die. Either alternative is bad. Good luck to her.