Miranda died in my game, how do I save her? Is it possible to do? I don't have any saves older than the one for the mission, am I screwed?
Apparently you have to have gone and met her at the Citadel earlier on, and warned her about Kai Leng (she sent an email way earlier on asking to meet). The reason she is dead is because Kai Leng killed her, although it's not very obvious from the scene - the same thing happened to me and it is far too late to save her now.
To save Miranda, you MUST read the dossier on Kai Leng and meet her via a holochannel from the Specter terminal after the attack on the citadel.
During the mission, she may also die if you do not persuade her father to back down. If that fails, you have to shoot him. If Miranda shoots her father, then she be fatally shot in return and die.
If Miranda is your romance in Mass Effect 2 and you break up with her the first time you meet her in Mass Effect 3, then she will die no matter what actions you take in Mass Effect 3.
If you continue the romance, or did not romance her in Mass Effect 2, then you need to give her the Alliance resources she asks for in the apartment in Presidium. Continuing the romance does not mean it is locked in - you can lock in with another character later - it just means that you should not explicitly break up with her when you meet her the first time.
Hmmm i dont know. I have played through twice so far and both times talked to her about Kai Leng and she did not survive either playthrough. My hypothesis is that she has to be a past romance or at least in an imported save from ME2. Both playthroughs I have done so far have been default non-imports.