Hell, if we're throwing speculation, who says Traya has to be female? I've several male candidates for the "betrayer/betrayee" position.
Exile would be the most logical candidate. Betraying the Jedi by going to war, s/he betrays Revan by walking away and coming back to face judgement. Taking the LS path, s/he saves the Masters, only to have them betray her/him by trying to strip away the Force (or worse).
Male Revan: Is there a party he DOESN'T betray sometime? He starts off by walking out of the Jedi, then betraying the Republic, then betraying the Sith faction he started. If he flips like a =/-6 card once those memories come back, who's gonna be shocked?
Atton Rand: Speaking of flipping like a Pazaak card...Atton started out Republic, went Sith, then abandoned the Sith. He's not so much a betrayer as a deserter, though, if he gets it in his none-too-stable head that Exile betrayed him?
Mical: Now, this might get really interesting. He's seen as such a goody-two-shoes (even if Exile corrupts him) that it might actually be a shock. There might be just a little feeling of being betrayed by the Jedi, after being raised by them, believing in them, and then "Sorry, kid, not enough masters." Exile could also "betray" him, either by going DS (ruining his image of a chilhood hero), or abandoning him to go chase the True Sith. Kreia also did backstab him, and he was a spy for Carth or Cede all along, so Mikey isn't as innocent as he looks...
Under the "They'll never go there, but it'd made a hell of a mod or AU fanfic"...
Carth longest shot. There's just enough weirdness in K1 to leave you wondering if the man's lit. Knowledge of betrayal? See Saul Karath. Betrayed in his heart? Check. Again, see Karath. Sith!Dustil AND either gender Revan could add to that brew. Will betray in return? Well, to many in the Republic, I'm sure that befriending Revan counts. LSF Revan adds an additional cringe factor by putting him in bed with the indirect killer of his wife. And if he ends up at the same place as Goto, concluding that he can't save the Republic while holding to its laws?