Almost every writer projects into Rei what they WISH she would
do. Be more emotional, suddenly confess her love, whatnot, etc.
That's not unreasonable, but there's a string attatched.
You've gotta set loads of groundwork and a
suitable explanation on WHY on earth she'd
go so badly Out Of Character.
Now, on the other hand, if you're willing to work
with Rei as she is in the anime, here's a few tips.
1) REI IS (usually) NOT VERBOSE
If she can say it in five words or less, she will.
The less words the better, and don't make it sound
too smooth either. There's an odd sort of stiffness
to her tongue, not quite robotic, but not your average
teen either.
1a) REI WILL HAVE SUDDEN BOUTS OF PHILOSOPHICAL INSIGHT
See the episode where the three kids work together
to save the town from a dive-bombing Angel. This
is the ONLY time Rei will spout out very long sentances.
2) ACTIONS SPEAK LOUDER THAN WORDS
With Rei, little things speak volumes, so feel free to
write in detail the slightest little thing. A lift
of the eyebrow, an ever-so-slight frown, a hint of a
blush. Don't overdo it though, else you cheapen the
effect.
3) REI WILL MOSTLY SPEAK WHEN SPOKEN TO
Rei talking of her own initiative is rare. It happens,
but even then it's usually prompted by something else
(another character is puzzled, she's commanded to
relay a message to someone, etc).
All things considered, there's really not that much to
work with, which makes writing a properly IC Rei a real
challange. What else can I say? Good luck and get
to it.
-Rod M