I'd estimate her age to be mid to late twentyish while the original would be more something between 18-22.
edit: so we are definitely on the safe side when it comes to perverted sex stuff with her ;-)... no mistaking here that she could be underaged ;-).
Ehm, guys, sorry to intrude, but I suggest you go back to the game, and check the "notepad", there, you will see her age.
I pointed it out to Limpy, while talking about an an idea for a game I am developing (it may never be distributed or even completed, though I have shown some ideas to Limpy), and he also had a wrong idea about the age of Rachel, he told me he had not realised her age, till when I pointed it out to him.
Just one hint, it seems Combine took some of his idea from Japan (I even though he may be Japanese, but I may be wrong), and AFAIK, at least some of the "Sailors" (I discovered there is more than one, I am not especially a fan), are high school students...