He sees Melina on the monitor because he's hazy and going under, and that helps cement her likeness as part of the final implant.
I think the image of Melina on Rekall's monitors was put there by the filmmakers just to introduce enough uncertainty to make the audience wonder if the events of the movie are "real" or not. But that explanation works fine for me!
Yeah but that would not be a proper memory then. It's "The memory of a lifetime, Rekall, Rekall, Rekall."
You're not supposed to dream your vacation, you're supposed to remember it like you've been there for real.
Exactly. If Quaid had memories of things that he couldn't possibly have witnessed, then he would immediately know it was a false memory, and they'd have to give him a full refund.