She tells the hero that one of the major cornerstones of his entire moral code (in this case, his "no kill" code) is wrong, and he accepts it,
while at his lowest ebb, and then, later, when he's pulled himself together, he goes "no what's wrong is wrong" and decides to take her in for murder and hand himself over as well.
You act like this is the first/last/only time someone in the Batfamily has dropped the ball when it comes to the "no killing" code. Anyone remember the times when Batman tried to kill Joker? Or the one where he tried his damndest to kill Ra's al Ghul? The point is, he bounced back and took her down like the villain (well meaning in some ways, but still a villain) he eventually realized she was.
As I said elsewhere, twice, Tarantula's story ends with her acting like a selfish cowardly bitch, trying to kill Nightwing herself, ultimately defeated by a Nightwing who, after resolving to the right thing, absolutely demolishes her with laughable ease.
She didn't "one-up most of the Bat family", as some people have claimed, she was a rookie that managed to keep up with them and occasionally surprise them (particularly in public venues where they couldn't respond to the fullest of their abilities). When push came to shove, Nightwing was able to defeat her while in crutches.
And she proved that, while she may have gone after people that were even worse than herself, she was a rotten person too, quite willing to kill a good man that she claimed to have feelings for, in order to avoid jail.
This is a "self insertion character"? Seriously?
Maybe for someone that needs psychiatric help, someone with deep seated self-loathing, someone that thinks they're evil and deserve to be in jail. But I don't buy it. I'm not defending this story, it was often VERY bad, but the "self insert/wish fulfillment" interpretation strikes me as the absolute worst kind of rabid fanboyism.