After spending five years apart on Pretty Little Liars, Aria and Ezra found their way back to each other. However, as soon as they seemed to solidify their relationship with an engagement, things began to pull them apart. There was news that Ezra's missing ex Nicole might still be alive, so he jetted off to South America to find out the truth. Nicole's disappearance had been weighing on him heavily and his mourning had only just ended when the possibility of her being alive was raised once again. Aria sent him off despite uncertainty over what the outcome would be. Now it turns out Nicole is alive on Pretty Little Liars, which could change everything for Aria and Ezra.
Aria found out in just about the worst way possible, too. Ezra didn't return home when he was supposed to, and Aria couldn't even find out if he'd gotten on his return flight. Then she turned to the television and got an eyeful of Ezra and Nicole's tearful reunion, complete with a kiss. Aria already had insecurities about Ezra and Nicole, so seeing them actually in each other's arms is bound to play on all her deepest doubts.
Aria's fear is essentially that Ezra is still in love with Nicole; she told Jason as much when she told him Ezra and Nicole would probably still be together if nothing had happened. And while it's understandable for Ezra to get swept up in the emotions of seeing someone he loved pretty much come back to life, the whole kissing thing was really not the best way to handle it. Particularly with a camera crew there to frame it like the romantic final scene of a movie.
This could mean big things for Aria and Ezra's relationship. He might not be quite so eager to rush down the aisle with Nicole back in the picture, but even if he is Aria's doubts might push them apart even further. Those doubts might push them so far apart that Aria ends up back in the arms of the recently returned Jason DiLaurentis, who is undeniably still all aflutter for her.
It seems kind of unlikely that the show would jump ship on Aria and Ezra after seven seasons of back and forth on their relationship, so odds are Nicole and Jason would just be pre-wedding roadblocks. However, an ex girlfriend returned from the grave is a pretty big roadblock. Aria and Ezra might have some trouble getting over this one.