I'm not surprised. That's what the League of Assassins does. What they don't do is offer to help people like she is, which is why I'm watching her.
Keep letting her appear? As far as I know, this is the first time she's been here. I'm afraid the situation isn't black and white enough for me to tell my team to storm in after her, especially not when we have bigger fish to fry. Where I'm from Talia's downgraded herself to an annoyance with questionable morals. I don't like her, but she's not the Joker and doesn't warrant the kind of stopping I suspect you're talking about.