Does It Actually Works?

I always hear it on people asking like this: do diet pills actually work? Fortunate enough to some it works but to some I feel so sorry. I have a cousin who really wanted to go on diet pills but it really didn't work on her. I don't know the reason behind, maybe she doesn't have any discipline on her food intake while taking the pills. She even told me that she's willing to spend money just to lose her weight and have a body just like me. lol.