Would we be able to play if she got a new psn account with a different region?
She would be able to play with you online simultaneously if she had a new psn account and her own copy of the game, you do not need a different region. --- "[...] her adult design was excellent." - Laevant
My brother and I both have the same PSN ID on our Vitas (I bought him his Vita, and am rarely if ever online). Only one Vita ID can be online AT ALL at a time, if the other one goes on, the first is kicked. This goes for anything, friend's list, the shop, online in a game, whatever.
However Soul Sacrifice has Ad-hoc multiplayer; a feature I used all the time with my brother while playing. If you're in the same room, you can play together on the same ID at the same time, but online features are disabled. --- http://www.explosm.net/comics/657/