Johnny Ringo said:
I dunno, wouldn't that mean Cavil and co. knew all along that she was one of them? - seems a bit odd. IIRC the actress [Kate Vernon] mentions she was in a few episodes this season...

"Now I’m in seven of the last nine, and they are just absolutely brilliant. I can’t tell you how good they are..."

That would imply she is in every episode from this point on.

I am willing to bet Cavil and co. did know all along (or since the point she died) that she was one of the final five, but that they decided to keep it under wraps.

It feels like so long ago since I have seen season three and the first part of season four. So spread out it is hard to keep up with stuff, but if I remember correctly, the rebel models were the much more touchy feeling, emotional, religious models, while Cavil and the others seemed not to think very highly of this character trait in them, right? It has been since pretty close to their air dates that I saw any of the episode prior to this half of season four, so I am a bit foggy. Since the final five was something the religious Cylons were always prattling on about, I can see Cavil going out of his way to hide her from them, just like how he boxed up ol' Xenia for having seen the final five.