But... a Bioware writer specifically addressed Kelly's ending at PAX (taken from the Bioware forums, who was quoting someone else).
-Did anyone on the Citadel survive?
Yes. We would never, ever do
anything that made the player feel, on replay, that it would be better for
everyone on the Citadel if they just died. The Citadel has emergency shelters
and kinetic barriers - even if it blows up, millions might survive. You
should assume that everyone plot-important on the Citadel survived.
-Is it better for Kelly Chambers if we talk her into
No, see above.
Please also note that Kelly was described as plot important. So there.