The key is that once she got her town back she kept on stealing, and with no guilt about it. We're also not talking about petty change here. Lastly, what is she doing right now? We just got more evidence of her robbing people blind.

Sure, if you can tug on her heart strings, Nami will help you. That's really not a big deal. I encourage you to look at Rich's articles on gaming, in particular about how evil characters can still have friends, etc.