C) Rhea's just a great character and it's disappointing that her story in Trek lit is over.
If the only characters who ever died were faceless redshirts, it wouldn't have any emotional impact, would it?
I actually think this is the one level on which Rhea's death did not
make sense. Due to the way she was used in this story, I think that the loss of Rhea is felt less keenly than is the loss of her character potential (particularly as relates to a potential future with Data). Obviously YMMV, but I'm not sure I would characterize Rhea's death as one that puts a face to faceless-redshirt-type deaths (if that makes any sense), nor would I say that the reaction it provoked in me was quite an "emotional impact."
Also, I've said this before, but I'll repeat here:
I think it would have been much more interesting for Rhea to have remained alive (through whatever means) and then have Data raise Lal with her. Single parenthood is not exactly a underused story in Trek (see Wesley, Riker, Troi, Jake, Kira, nuKirk...) and it was honestly a little disappointing to see David Mack
not shake things up a bit. (Reminds me of my disappointment with Michael Martin's decision
in his last Titan