"Hold on, I have to check something. I'll radio you back."
In 2005, Rachel and her partner Raymond Vester were sent to the Queen Zenobia and got separated due to their missions. While Rachel headed to the back of the ship, Raymond headed to the front, though along the way she acquired the key to the freight lift. Whilst looking around Rachel discovered slime before being ambushed by an Ooze and shot the creature several times and when Jill entered the room, she had already escaped. The creature followed her through air vents and Rachel ran into a hallway with more Ooze. She shot again, only to run out of ammo and throw her gun on the ground. Rachel managed to get away and reach the elevator where she was ambushed by another Ooze which cut her leg. She avoided death one final time as the elevator doors opened, allowing her to escape and lock herself in the research room. It was in the research room where she met her end. Surrounded, Rachel was choked as an Ooze fed on her bodily fluids and infected her with t-Abyss, finally throwing her at a window. During this time Jill was looking for the Crew Quarters key and arrived just in time to witness her death.
Rachel's intentions on board the Queen Zenobia were seemingly to investigate and transfer the ship for disposal, unwittingly to erase any evidence on board that might incriminate Morgan. Later on, when the player gains her journal, it becomes known that Rachel actually did not want to go on the mission and had a very grim and pessimistic view on her survival chances, a prospect that grimly became very real.
Shortly after her death, the t-Abyss virus kicked in and mutated Rachel into a seemingly unique Ooze. As Jill returned to Rachel's corpse to find the freight lift key, she noticed that her body was gone. Jill left the room and was attacked by Rachel, now mutated. She confronted Jill several times, always fleeing after taking heavy damage, but Jill continued to encounter her until she met up with Parker and the pair supposedly killed her.
However, Rachel survived the encounter and frequently attacked the duo as they explored the ship (which greatly annoyed Parker). She was incredibly resilient to gunfire, being downed several times after Jill and Parker initially "killed" her.
Rachel was presumably destroyed permanently when the Queen Zenobia exploded.