Did it make sense for DC to kill the original Supergirl?

Am I the only one who thinks they shouldn't have killed off the original Supergirl in Crisis On Infinite Earths? The reason DC gave for doing so was to make Superman unique, but they just brought in a new Supergirl (the "Matrix" Supergirl) a couple of years later. And now we've got a Supergirl who is once again Superman's cousin from Krypton. It would have been a lot less confusing if they just kept the original Supergirl, and had Donna Troy/Wonder Girl sacrifice herself fighting the Anti-Monitor. After they rebooted Wonder Woman as a newly arrived superhero, Donna Troy no longer made sense. So they had to keep giving her new origins (Titans of Myth, Dark Angel, etc.) in an vain attempt to fit her in the post-Crisis DCU. I wonder if DC considered making Donna Troy the "sacrifical lamb" instead of Supergirl, since they were going to reboot Wonder Woman? Or was the decision to reboot WW made at the last minute?