She tried to follow the bison, but failed when night was around. In the morning she had no idea, where she was and where she should be heading. Sun decided in this case it was probably the best to just follow her feeling, her father would guide her wherever she would be needed, hopefully.
She stepped out forcefully and continued on her way.
After three days of walking she was tired and exhausted, she had not walked for that long all her life. The path before her looked the same as everyday, but her steps grew smaller with each passing mile. Her mind felt dizzy and so she nearly fell into nowhere. She jumped backwards screaming. The cliff was quite surprising. It took a few minutes for her breath to return to a normal state. She looked over the cliff. There was just fog, deep down, and Sun wondered if there was a bottom at all. Then suddenly everything went black when the earth opened beneath her. She gasped when her fall came to a sudden halt. Around her was light again, but her body stuck in the earth, she could not move a single muscle down from her throat. She held her eyes closed tightly, then she slowly opened first one and then the other and faced a surprised Gaang.
A girl in clothed in blue came a few steps towards her. She talked in an almost angry tone, "Who are you?! What do you want here?". It took Sun several moments to remember how her tongue worked, but then she replied quietly, caused by a suddenly very dry throat, "S-Sun. My name is Sun.".
"Do you want to mock us?", the girl in blue got even more angry. Now Sun was starting to get angry too.
"No, I don't want to mock you. It is just my name if you would allow, thanks. I followed two boys and nearly fell down the cliff. Enough explained, Mylady?", she spit the last word out, very unlike it's meaning.
She saw the girl was now infuriated, but was interrupted by the other girl next to her.
"Stop it, Sugar Queen. It is Aangs business to deal with her. He is the Avatar, he will decide.", she stated simply, while "Sugar Queen" stormed off.
When she was gone the other girl said, "Hi, I'm Toph.", "Nice to meet you Toph."
"Your name is really Sun?"
"Yep. I can't help it, it can be quite a burden, sometimes… "
"I think so too.", they chatted happily until Sugar Queen and the little monk she saw in the village came up to them.
"So, your name is Sun?", he asked doubtfully.
"Yes. I followed you and the Fire Nation Prince from the Sun Warrior village."
"Is she alright?", he asked Toph.
"Yes, everything she said is true. Or she is as good as Azula when it comes to lying."
"Okay", he turned to Sun again, "What do you want?"
Sun smiled broadly, "I want nothing but to make the world a better one, to help you on your further journey."
They all looked somewhat skeptical. So, she added, "I had a dream in which my father said, "The Avatar and the young Fire Nation Prince will need your help when the time is coming", but then I already followed your bison and was already on my way here.", it did not help.
To everyone's surprise she suddenly beamed out of the earth she was kept in. Sun landed gracefully on her feet and smiled at Toph. She smiled back, "Whoever her father is, I think we can use any help we get.", and towards Sun, "Come, I will show you an empty room."
She followed the Earth bender into the building, leaving a perplexed Aang and Katara behind. While walking she asked Toph, "So, where exactly are we, and what do we do here?".
"Basically we are in the Western Air temple. And we are preparing, training for, uhm, I do not know exactly for what, but I guess some kind of final battle."
"Ah, okay. How can I help?", that brought her a punch in her arm from the tiny girl.
"I knew, I'd like you, whatever you are. I think you can help Sugar Queen, uhm, Katara, prepare the meal when you are done with moving in. She will be somewhere outside, cooking."
"Where are the others? There must be more people than just you three. And where is that flying bison?"
"Appa is on the other side of the courtyard, just over there. I'd bet he'll like you. You will meet the others at dinner, that is the easiest way, except for Sokka and Zuko, they're on a fishing trip.", she shrugged and left Sun in her new room. She looked around. Old walls, but cold as stone is, she was suddenly freezing. So the Prince was on a fishing trip, huh? Sun wondered what they would fish.