It is not that body fat loss is slow... Body fat can be metabolized as fast as your metabolism needs it. Rather, its that muscle gain is suuuuuper slow. Especially for women. If you lift weight quite heavily (and I don't mean those silly 5 pound dumbbells) you will be lucky to gain 1 pound of lean muscle a month.
1 silly pound!
And you need to gain muscle in addition to losing fat in order to see definition.
I started lifting weights 1 year ago.
So how does this relate to fat loss?
You are probably not "seeing" fat loss because your muscles need more time to develop. That creates definition and the look of having lost body fat. So right now, if you are in a calorie deficit, fat loss is certainly happening, its just that pound for pound, muscle cannot replace it as fast.
But for you, since you are already so small, it's going to take even longer to shed fat since you cannot healthfully create a very large deficit per day. From what you have described, your dress fitting differently, but pants the same, sounds about right in your time frame. In fact, I bet your pants fit differently, you just don't notice
Just be patient and lift more weights!