If you follow the hyperlinks (part one and part two) you will get to an excellent article from Ryan Hunter exploring what we can learn about the two queens, and their attitudes from their correspondence.
As he suggests, “Mary, Queen of Scots and Elizabeth I’s letters to each other were their only sources of communication, and they remain to this day historians’ most insightful and formative sources on the quarter century-long rivalry between the two queens, as they show how Mary and Elizabeth’s relationship changed over time. They reveal fascinating insights into the two cousins and rivals’ personalities, and above all else, their fundamentally different approaches to their respective positions as two queens regnant living on the same isle with a claim to the same throne.”
Hunter divides the relationship into four phases – have a read, and see if you agree. For those of you that want to push yourself, the full essay A rivalry in Letters can be found on his excellent blog.
Mr Kydd.