When is the "lock-in" point for the Diana Allers romance?

Generally, in Mass Effect, you're limited to monogamous romance. However, Diana Allers seems (from what I've read) to be a little unique.

• The Mass Effect Wiki entry for Diana Allers notes that she does not become a "committed partner".
• The Mass Effect Wiki entry on Romance does not include a "lock in" point for the Diana Allers romance.

As it is now, I've done a bit of mostly harmless flirting with her up to (and including) the second interview - the one where she says she might follow me home like a lost puppy or something. However, my end goal for this particular version of Commander Shepard is to be with Liara.

IMPORTANT NOTE: I'm not seeking to actually romance both characters - i.e.: reach the final love scene or establish a permanent relationship with both. I've just been perhaps a little too friendly with one person than I should have, while I'm intending to pursue another.

Have I gone too far with Diana for me to have a successful romance with Liara, or is there actually no point of no return (besides the final romance scene) with Allers like there is with the others?

Solution 1:

From what I have managed to gather, the lock in point is the third interview scene. After this, other characters will consider her "locked in". As such, Liara and others will call you out if you pursue relationship with them after this scene.

However, she is not considered "full" romance option and as such does not give an achievement. There are also some weird things, with some characters noticing your relationship with her and others not. As such, her "lock in" point could be considered buggy.

Also, if you are already committed to another romance, you can't proceed with Allers. As such, concentrating on other will help you strafe off Allers.