Hunted down by who? Law enforcement? They did, and I noted she was at large during that time. If the problem is her getting away at all then I understand.

In any case, being a pyromaniac is a defining aspect of her character. I can see how it would mean she'd be sought after by heroes aware of her presence after the Awakening, but the period between her Awakening and getting arrested in Europe was short. I don't think it's impossible that individuals just didn't get to her during that period.

If the problem is her pyromania getting in the way of actually being accepted into the League, then I'd just like to point out that she's clearly indicated her intent to turn a new leaf, and to direct her tendencies to more useful purposes. If there are anti-heroes in the League already, I don't see why she couldn't make it in.