Maybe she was brought back because it costs more to "make" a new one.
As near as we can tell, Cylons do not have any kind of economic system other than what's necessary coming first, and what they want coming next.
There's a big complexity going on with Boomer. Keep in mind that the reporter girl has brought back critical information, but isn't a hero. So she could be jealous. But as Six pointed out (And I think we can take this as being pretty accurate) they're celebrities in a unity-based culture. The Cylons seem to have a very communistic style of life (see economic comment). But seeing as how the Cylons view the revenge on the human race as an important goal, they become special for their achievments. But other Cylons, presumeably the ones in power, do not want them to possibly change the opinion of the other Cylons, and introduce chaos.
Finally, there's the whole resurrection thing. Which would seem to be very important to the Cylons. Think of how defensive people get when someone mentions Social Security. How defensive would those people be if you started knocking off people's chance of resurrection? They'd be afraid of the same thing happening to them. And in a unity-based culture, unity and cooperation are going to be important. So if it's some master computer giving orders to the Human Cylons, it needs them cooperative, or the culture goes bye-bye. If it's the Human Cylons giving orders to themselves, then it has to be done with the cooperation of the others - or else it could spawn factions, and crack or even shatter the unity.
