Thank you and excellent question. The pregnancy alone will be the first bombshell hit. This should cause both player and the player's character to start to wonder about themselves. Can a human female conceive with a replicant or is that evidence that the female must also be a replicant? Who knows? (remember there is a huge school of thought that Deckard is a replicant, a school that includes Ridley Scott)
At some point there should be a huge reveal that confirms she is a replicant (2nd bombshell) and an immediate reduction of her resolve coupled with probably 3 stress points. ie. she SHOULD be broken by stress right then and there for a bit.
How to do the reveal;
Since she has been on the force so long, her significant relationship is actually Holden who has been like a father figure to her. The reveal could come in the form of a VK test by Holden or another RDU veteran or old timer. Also it could come from the OBGYN seeing serial numbers on her when examining her for the pregnancy. She might initiate the test to see if she is a replicant. Maybe she approaches Wallace or the Replicant Underground?
Much will depend on her reaction to her pregnancy, which I don't know what that will be. Like a real person, she has to decide if she will carry it to term or terminate it. LAPD is open minded enough to grant her leave and she can afford daycare if she keeps it. If she does not keep it, someone is going to find out because I am a GM who likes to see a crisis.
The big conflict for her in the immediate is the fact that she knows that the baby is at least half rep. What happens if others find out? How would Holden react? What happens when Neander Wallace finds out? (which he will and Quell will return to cause trouble). What will the reaction be from the Replicant Underground that already knows about Rachel's child? Afterall, as Yoda said; "There is another..."
I am not sure what her end story will be. She and her child may not survive or they may disappear. Wallace will realize that N-7 reps have the ability to reproduce and that will cause Wallace to flag any inquiry into an N-7 serial number (this dovetails with BR2049 when K brings Rachel's DNA)
Some of the possible events could drive this campaign out of the movie Blade Runner canon completely, which I am prepared to let happen.
In the meantime, until another entity besides herself learns the truth, she is covered and can work case files normally. I will keep you posted on this thread of course.