Wrongly Accused of Assault in Texas

My question involves criminal law for the state of: Texas

My sister and her boyfriend were sent to jail and charged with assualt. While waiting in line at a drive through window, my sister got out of her car to speak to her BF in the car behind. The line moved forward but the car my sister was in did not move immediately (it wasn't their turn to order any way). The man behind them honked his horn, started yelling at them then got out of his car to confront them. By this time, my sister had gotten out of her BF's car to get back in with her friend so he started yelling at her. She yelled back and then he pushed her. Her BF got out of the car, pushed the man and told him he wasn't going to push her. The man threw the first punch, busted the BF's lip and so they started fighting. My sister tried to break it up and the man threw her against the car (She has scratches down her back because of it). When the police showed up both my sister and her BF were fighting with the guy. The police separed them, took my sister and her BF to jail and sent the man that started it home without a ticket or anything. I'm not sure if you think this matters but the man that started it is caucasion late 30's early 40's, my sister is caucasion late 20's and her BF is african american late 20's. They had to spend the night in county jail and are now facing assault charges. What do they need to do to fight this? To me, it seems like it was self defense we just don't know what recourse we have legally. BTW, they do not have the money for lawyers fees.

Thank you for your time.

They should retain a lawyer, and find out what the police report says.

It wasn't "self-defense" for BF to get out of his car after the confrontation had apparently reached its culmination, and then to escalate things into a fist fight.