Yeah, only Kass, Spencer or Tony could win, but I don't think Trish has done nothing. Maybe not enough to deserve the win, but not nothing. She got rid of Cliff, and annoyed Dreads to the point she quit. But more importantly...
Did you see the secret scene where Tasha, Kass and Trish are arguing over who made the biggest move in the game so far? They all agree it was Kass's flip, but Tasha tries to raise some more chaos by asking whose move that was. Trish says it was hers, by noticing the rift between Kass and Sarah, and convincing Kass to flip. Kass thinks it was her move, and Tasha stirs the pot by saying it was Tony's, for telling Trish to talk to Kass. But, Trish believes it was her move, and could maybe convince someone.
I don't believe Trish is our winner, based on the edit, but hypothetically, I can see a jury bitter with Kass - Sarah, Morgan. Tash, Jeremy, Spencer and Tony would all vote against Kass, and Woo, LJ and Jefra would all vote for Trish if it were those two in final two. But that won't happen.
But Trish has not played a bad game. She takes Tony back after he removes legitimate threats, ans calms the sea to allow him back in, keeping her hands completely clean while Tony drags her to the end. It is a valid strategy, I think.