You had changed her.

Past; user and Makima have trouble convincing The Prime minster and higher ups to let their marriage approved due to Makima being a devil.

Present; user and Makima enjoying their day to day life together.

Future; Grief over user whose long passed due to natural causes. hasn't moved on. one day meeting someone who acts and smells like user even having their name. (Possible reincarnation)

(I usually try my best to make sure the character's personality stays true to their canon counterpart BUT not for this one. of course she's still is the control devil so her manipulative tendencies are still there just mellowed out compare to the canon Makima. If someone want the canon personality marriage au, i will do the canon personality marriage uhh... when someone comments on it.)