maximumphilosopheranchor:

Mary didn’t ratify the Treaty of Edinburgh that
officially declared Elizabeth the monarch of England, she never gave up
her claims to the throne of England. Even Henry III of France in the
1580s came to appreciate it and urged her relinquish them to improve the relationship with
Elizabeth.

Mary wanted to be openly recognised as Elizabeth’s heir but
Elizabeth although preferring Mary over the Grey sisters had her own sound
reasons against naming the successor. Neither was prepared to budge on this issue.

After
Elizabeth inherited the throne Mary started to use the arms of England
in her heraldic devises and the title of queen England and Ireland. She
continued to do it after becoming the queen consort of France and didn’t
give a damn about Elizabeth when her father-in-law and her husband
threatened to invade England in her name. Moreover, Mary signed away
Scotland to France and the French presence in Scotland meant that
England could be attacked by France from the north. It was
not a small matter and Elizabeth had every right to distrust Mary who was a total stranger to her. None sensible ruler would
have taken Mary’s later words- words that costed her nothing- at face
value after this. It was Mary who had designs on Elizabeth’s throne, not
the other way round, and Elizabeth didn’t owe anything to her.

They were no sisters, and they never came to be friends.

Elizabeth
would have been content if Mary had dropped her
open pursuits of the English succession and ruled Scotland married to somebody
friendly to England (hence her offer of Robert Dudley). She wanted peace with Scotland and she did try to establish a normal relationship with Mary.
Even after Mary was deposed by her Scottish subjects and escaped to
England Elizabeth negotiated with the Scottish government for Mary’s
reinstatement (which was more than anything Mary ever did for Elizabeth)
and, in my opinion, she has not received enough credit for that. But
naturally in doing so she was not prepared to sacrifice her own
interests for the Mary’s sake and eventually to set free someone who plotted to dethrone her welcoming foreign invasions.

Also, it
perplexes me that Elizabeth in popular imagination is often seen as this
super power-hunger ambitious ruler who wanted to rule Scotland
when in fact it was Mary who had ambitions to acquire kingdoms (England)
that didn’t belong to her.