Who deserves to be first and second author? PhD student who collected data, research associate who wrote the paper or supervisor? I am composing a manuscript using data collected by a PhD student over two years. She doesn't have enough statistical or analytical skill to publish her work. On top of that, language is also a huge issue for her. 

I redid the analyses, created the graphs and started writing with my own flow and conclusion. I am also receiving supervision from a post-doc who got his PhD in the relevant field as the topic of the paper while I don't have much experience on the area. 

I am quite confident I have the right to claim as the first author but when I allocate the second authorship to the post-doc, the student was acting up with me. Without me writing and the post-doc supervising, she will never be able to publish her work. So, who really deserves which? 

Updated : Let me clear a few things here. I understand the conventionality of assigning authorship here in the US or other advanced countries. PhD student is from a country where even young faculty doesn't know what peer-review publication is. Post-doc(the supervisor) and I (research associate) are based in the US. PhD student collected the data 3 years ago and she and her adviser came up to me to collaborate on research projects and she handed the dataset to me to write. She has no interest in taking part in the writing process (no phone call, email or no showing of desire to learn anything from the process). When post-doc and I started writing, there is not even a promise of her data and research design can produce anything. We had to recraft research questions, redid analyses, graphs and everything. It was much like you download the someone esle collected data from public website, you write analyze and write a paper on it. During my Master year, my US adviser used the 10 years dataset from a peer who collected the data but didn't express interest in writing it. The guy offered us with the data, we wrote it and his name came as 3rd author. Seriously, we don't even know this paper can even be publishable and we are just making the best out of it.
Put yourself in the shoes of the PhD student. She spent 2 years of her life conducting a study and collecting data. She needs help with statistics and writing (this is very common). The person helping with this claims first authorship (in my field this is already questionable) and on top of this even wants to give the second authorship to their supervisor. I can't see how this is supposed to be fair to the PhD student. The post-doc at most deserves third or fourth author. Where is the advisor of this PhD student? You are doing their job (and in my field the advisor would be last author).