After the fact? Possibly, maybe even probably. I don't see how it could be coincidental, unless you're trying to claim that they somehow arrived at that point randomly, which seems far-fetched. Sure, they didn't do anything interesting with it, but the same could be said of a dozen different plot points that season.
A) Story structure: Seasons 2 and 3 are both built the same way, with two distinct halves, split by an episode which clears the board in a comprehensive and more-or-less unexpected manner ("Phase One"; "Full Disclosure") and which notably end the same way: with a twist introducing a female double agent with a personal relationship to the good guys, who then spends most of the back half of the season operating covertly.
B) Their placement as dark reflections of Sydney, in ways more direct than say, Anna: Allison is the Project Christmas graduate who's a double agent in a situation she hates, and is in love with her handler (Sark). Lauren, as mentioned, has an inverse of Sydney's family structure.
C)
You could say the same things about Allison, who was suddenly gifting Vaughn neck ties for no reason and (especially in the first episode after the reveal) made up way differently.
Again, none of this is actually conclusive evidence. But a case can be made, and if the writers have claimed that the reveal was planned from the start, I don't think there's any reason to disbelieve them, particularly since "being planned from the start" has no direct bearing on whether a story is good or well executed--just ask How I Met Your Mother fans. Or heck, just look at the resolution to the "two years" story. Sure, all the evidence we're given through the season points to the solution that we're eventually given. It's still a hella dubiously executed story.
