Not sure what I need to purchase?

[maxaud]

If you will only be playing the PS3 version when your wife isn't on it, you only need to buy 1 PS3 version of the game but she does need both a separate PSN and SE account.

I don't think this is accurate. From what I'm reading, I'll need two PS3 copies of the game as once the first version is associated to my wife's service account, I can no longer associate to mine even using a different PSN network ID.