It's a war between Muslims. And Muslims have been fighting against ISIS since late 2013 (perhaps prior to that too, but that's when relations in Syria between rebel groups and ISIS became much more strained because of some killings). 700 Sunni tribesmen were killed by ISIS a bit more than a year ago because
they openly refused to pledge allegiance to ISIS. Muslims are fighting ISIS with their hands, with their tongues, and likely with their prayers.
As for the topic, doesn't she fit the description of a lone wolf? Neither she nor her husband were directed by anybody. ISIS didn't even know about it (but of course cheered it on).
Also, jihad is not what this woman did. She may have said she supported it, but she had clearly had no idea about the rulings that it entails. Apparently she did not know that the guidelines it sets include not intentionally targeting non-combatants and not betraying covenants (her entry into the US was a covenant and her husband being born here and being a citizen was a covenant). I'm just a layperson and I could've told her all this. What she and her husband did was completely against our religion.