(A/N: I was planning on clarifying this in the previous chapter but forgot, basically Soza had a very deep connection with he Chi, and the Chi of others. She can sense the heat around her and that is how she 'sees'. It's similar to Toph in that way :)
Soza couldn't see well at all. Everything was so hot it was hard to tell anything apart. If she attacked she might hurt Appa.
"What are you waiting for!" Toph yelled, "Stop them!"
"I-I can't see. What if I hurt Appa?" Soza stuttered, "It's just too hot. Everything jumbles together."
"Heated up sand makes glass right?" Toph yelled out.
"Yeah, so?" Soza replied.
"Heat up the ground so I can see and then I'll fight!" Toph said. Soza nodded and began to set the ground aflame.
"A firebender?!" one of the sandbenders yelled. "The Fire Nation took everythign from me..."
A few of the benders began to run at Soza.
"Please stay back! I don't want anyone to get hurt!" Soza yelled out.
"Didn't feel that way when my fiance was burned to death!" One of the roared back. They began to wrap sand whips around Soza.
"D-don't make me do this!" Soza cried out as the sand dug into her skin. Finally she released a deadly burst of flame from her mouth, burning the benders near her. She tried to close her mouth and stand but the flames just kept coming. Soza fell on her back and began to sieze up as fire roared. The sandbenders left with Appa as everything around Toph became increasingly hotter.
Finally, Aang, Sokka, and Katar exited the temple. Toph prompty dropped it and backed away from Soza.
"What's going on?" Katara asked, staring at Soza's writhing body.
"I don't know. One minute she was fighting o-"
"Where. Is. Appa." Aang said, staring at the endless sand in front of them.
"The temple was falling, so I held it up. Soza tried to fight of the benders, but it was hard for her to see with all the heat. They began to attack her when they realized she was a firebender and she lost control." Toph explained in a sad tone.
"We have to find him!" Aang cried out.
"I'm sorry Aang but we kinda need to help Soza out right now." Sokka said.
"I have an idea." Katara said, "but it'll take all my water and we might need it later..."
Aang turned to Soza and began to funnel the air around her mouth, taking all the fire with it. Soon she was unable to breath out the fire due to lack of oxygen, and passed out.
"There, problem solved. Now it's time to go find Appa." Aang said while the rest of the group just looked at him, stunned at what her had done.
"Fine, let's go." Sokka replied, picking up Soza's body as the group began to wander the desert.