The only people in the AR that can have flashes are the DEAD ones in the OR (except Desmond) by Zubieta

Come to think about this:

Current flashes:

-Daniel [dead in OR] with Charlotte (He saw her from some distance in the Museum)
-Charlie [dead in OR] with Claire (He might have seen a little from her)
-Desmond with Penny [Not dead, but he's special and was submitted to the Electromagnetic Room]

And flashes that haven't happened (but should have happenned):

-Jin with Sun [They are definitively their True Loves, but Both are alive in OR]
-Jack with Kate [They saw each other in LAX, but Both are alive in OR]
-Sawyer with Kate [They saw each other in LAX & the alley, but Both are alive in OR]
-Rose with Bernard [They were flying together, they are married, then maybe they are still alive in OR]
-Locke with Helen [Must be because MIB is impersonating him in OR, retaining his memories (remember that FLocke has Locke's memories)]
-Sayid with Nadia [He's still alive in OR, or at least Zombie-Sayid is Alive, So he couldn't have a flash when visiting Nadia]

(Nadia is dead but can't have flashes about because she never was either a candidate or in 815)

THATS BECAUSE IN ORDER TO HAVE A FLASH WITH YOUR TRUE LOVE IN THE AR, YOU MUST BE DEAD IN THE OR (except if you are Desmond ^_^)

Flashes that could still happen:

-Alex with Karl [Both Dead in OR]
-Charlotte with Daniel [Charlotte didn't see Daniel when he saw her, but that doesn't rules out she could see him in the future]
-Juliet with Jack [she's Dead in OR]
-Juliet with Sawyer [she's Dead in OR]

Juliet could be a special case because I'm definitively into thinking that she must be David's mother (Blue eyes, she is always absent (because she's filming V)

So maybe if Juliet were to be married with Jack in the AR, maybe she hasn't had a flash with him because, as timelines are happening kind of "Simultaneously", while she lived with Jack she was still alive in the OR (So no flashes for her), but once she died in the OR she wasn't with Jack, so next time they meet she could have a Flash, or simply Jack isn't her True Love.

Maybe her true love could even be Edmund Burke, but that would be awkward (he's a creepy guy!) or Angelina Jolie... j/k ;)

Hope you enjoy my theory :D