1) I'm guessing we need two separate service accounts, correct?
Correct.
2) Do I need a second copy of the Playstation 3 version of the game? One for her, and one for me?
Yes, one copy per service account.
3) Do I get the cheaper Legacy member pricing on the second service account I have if one is required?
No, only on the specific legacy account.


At least, this is my understanding.