How old is she, and how active? A young active cat will burn more calories than an older one that spends a lot of time sleeping (sorry I know that is stating the obvious!) Has she been wormed?
I can't advise about the amounts you are feeding as I'm not familiar with US measurements, Science Diet is not the best there is and they will eat more of it than a higher protein food, but as it was free and what she is used to then there is no harm in using up what you have before gradually switching her to something better quality, which she will need a bit less of.
With my greedy boys I split their daily rations into 3 small meals, spreading their feed like this helps to minimise begging and pleas of starvation - they are getting the same amount of food over the day. My belief is that this fits better with the natural behaviour of a predator that would catch one small meal at a time and go out hunting again when next hungry.
Don't forget that moderate hunger is a normal part of life, it's the body's signal that it is time to look for the next meal, and it is neither cruelty nor neglect for your pet to be eagerly anticipating her meal when it is served up.
I think in the long term getting her onto a higher quality food will help, cats can have problems getting proper nutrition from the high cereal content of foods like Science Diet and it can leave them wanting more, hopefully others familiar with US measurements will be able to give detailed advice about suitable feeding quantities
It is also likely that she is asking for attention, playing with her using interactive toys such as wand toys or toys on strings that you can dangle for her will help her to feel fulfilled - a cat doesn't just eat, it hunts too, and a cat that has limited or no hunting activity may still feel hungry even if sufficient food is supplied, because in its mind it has not completed every part involved in finding and eating a meal - playing with her before mealtimes can help simulate that hunting experience