Judging by unused voicelines, she (with Leixia) ended up being brought to them due to:
A. Maxi has a Soul Edge fragment on his body.
or
B. Xiba has this 'evil' energy in his body, so he is always hungry.
We have already seen that during Libra Soul Taki ends up appearing due to the powers of Conduit, just as she tried to fight Kilik in Story Mode, probably Natsu is doing it for her, and ended up seeing that Xiba was harmless.
"I guess you're not evil after all. So who are you?"
I believe that if the game had been completely finished we would start as Xiba, Maxi, Leixia & Natsu and end as Patroklos, Pyrrha, Z.W.E.I. & Viola. But the budget and time ended up giving us only Patroklos, Pyrrha and Z.W.E.I..