WI Mary I had not died from cancer in 1558, but insted had lived at least as long as her father, dieing around 1570? What would happen to Elizabeth? Would Mary be more succesful in bringing England to Catholicism? And how would be her relationship to Mary of Scotland?
I assuming that even being healthier Mary wouldn't have managed to have any child, and Mary of Scotland would still be sent back to her country with her husband dieing childless in 1560.