In order to win I think she needs to hit a peak just at the right time. Unfortunately she's experiencing one now, almost 2 weeks away from the final.
Scotty is also experiencing a bit of a slump with Megan going and his role in the house not being quite clear. He's looking rather pointless, more than usual.
Tiffany does currently have a great balance going on - she's outrageous enough to appeal to the forums, hardcore BB fans and even younger viewers, but she's not being too outrageous where she alienates people. Her actions are seen as strange but fairly playful and harmless. Plus I'm impressed the way she's forming bonds while other relationships are breaking down.
But the dynamics in this series are so bizarre, changing all the time. Not like the last CBB where they were stuck and the winner was pretty much nailed on.
Now Tiffany has the unenviable task of keeping viewers amused with random behaviour so she doesn't lose existing fans or sink into the background, but she also can't go too OTT for people to get sick of her.