Confront the ESTP. I hope you aren't a person who is afraid of confrontation. Don't back down if ESTP tries to justify selfish behavior. It's great that you're an NT, so hopefully you can stay rational in the face of asshattery.
On the other hand, someone else made a very good point when they said ISFJ should speak up for ISFJs self. After the initial confrontation, if ISFJ keeps feeding into ESTPs bullshit, then maybe it's best to talk to the ISFJ about what ISFJ is allowing to happen.