Ha, I'm thinking she's less of a poker player, more really, really confused. 🙂
When Buffy becomes the enemy Faith seems to treat it as a game, like the two of them are the same, just on opposite sides, playing against each other.
Faith hurts Buffy and Buffy hurts Faith and, yes, Faith is willing to put plans into action to kill Buffy. (She's all for the Ascension, even though it will wipe out Sunnydale and kill all of Buffy's friends, and logically kill Buffy) but she doesn't want to kill Buffy personally and end the game. For whatever twisted reasons (admiration, jealousy, love) she wants her game with Buffy to continue.
She also 'brings forth' Angelus, to 'get one up' on Buffy, to take her guy away from her. The whole torture thing is the Mayor's plan that Faith goes along with, but Faith doesn't really harm Buffy, again like its all a big game to her.
It's only at the end of the episode we see Faith's confusion/hurt. She got played, she lost that round, and now there's no going back- she's made her choice, betrayed her friend and that's that.
Right up until Graduation Day Faith treats it all pretty lightly (kinda psychotic considering what she's done) and is surprised that Buffy comes to find her and (seemingly unflinching) says she going to kill her.
This even explains Faith's surprise and disbelief when Buffy stabs her (although some of this can be taken as Faith's confidence that she's going to win, and it is a pretty close fight) and her anger when she wakes up from her coma. ('You tried to gut me blondie.')
I think, in the end, all Faith had was this spiral of violence directed against Buffy that she didn't realise the extent of until it got out of control and it was too late.
