In the article, The Daughter Deficit, it mentions that it is rarely good to be female anywhere in the developing world today. Millions of girls grow up stunted physically and intellectually because they are denied the health care their brothers receive. this example portrays sexism, being unable to receive health care while their brothers get to, reveals that the boys are put as first priority in the household which shows us that they are considered more important or valuable than the girls. Putting boys as a priority can result in millions of girls not receiving proper health care or educational treatment, getting treated in inhumane ways, and can also result in millions of girls disappearing as the article mentions.
One thing that you will need to do is to ask if there are any explanations other than sexism and injustrice for this situation. What reasons might there once have been for people preferring boys? Do those reasons still apply? Are there ways to get people to stop having this preference for boys?
If you do that, you will have something more than an essay that just says "bad things happen to females in the devloping world and that's not just."
I think that you are on the right track in bringing out the idea of social justice in the article. I think that you need to go back to the article and "flesh it out" a bit more in terms of discussing the specific situations used. For example, I think that reverting back to the article and discussing the specific contexts or situations where daughters are denied health care would help a great deal. What situations did the article address? Where does this take place? In what context can this be seen? How does the article show this? Being able to use the evidence asserted in the article will allow you to make your link of sexism and the disproportionate treatment in question. The ideas of social justice are present in the analysis. Yet, I feel that you need to reference the article more and make it more about your impression to what is depicted in the article, as opposed to simply declaring what is seen to be injustice and unfairness. Once this is done, I think that your analysis grows in strength.