He comes first

One day, my conversation with my eldest child, Princess:

Princess: Mummy, why you always make milk for '"de-de" (brother) first?
Me: Because he wants to drink milk.
Princess: But I also want to drink milk. You never make milk for me first??
Me: De-de is younger, so I make him milk first.
Princess: Why always him first? I want to be first too.
Me: You know your brother, cannot wait and have no patience. You are big girl, you give to your little brother okay?
Princess: Hmm. (Sighing)
Me: Mummy love you and Baby Jay. You are big sister and big sister should love de-de too. Whoever first is not matter. You will still get your milk.

Now I wonder whether I am right over here? Or maybe I should try different way of approaching her question?