Woah! We've seen them kiss once and now that we see Aang kiss her for the second time, she is surprised and backs away and thats supposed to mean love? Backing away from a kiss given by someone everybody (not everybody except Kataangs) believes you reciprocate romantic feelings for means love? A hug even if its platonic is better even slightly than her backing away. I dont know but my conclusion would be that she's having second thoughts if she ever thought and felt like she had romantic feelings for Aang.

For what other reason would she back away? If she has romantic feelings for him she wouldnt back away. Maybe she backs away because she has no romantic feelings towards him or maybe no longer has them. The first time they kissed, she didnt back away but corresponded and now that Aang kisses her for the second time, she shouldnt be surprised but (if she had romantic feelings for him) correspond back. She shoulnt be surprised. So maybe she is having second thoughts if (and I repeat) if she ever thought and felt like she had romantic feelings for Aang.

The Hug:

Even if its hard to admit to everyone, Im going to say this: That hug means friendship....hopefully it might not!

After I saw the trailer, I was thinking about it and I concluded that she hugged him beause they were saying goodbye to each other before they went to war. The clothing we see them wearing when they are at war are the same clothing Zuko and Katara had when they hugged and she maybe hugged him because previously they might gotten the chance to put a halt to the misunderstanding that Katara had towards him and maybe before that hug ocurred he finally convinced her that he changed by finally doing something very important that proved to her that he changed. So if they cleared the misunderstanding then why wouldnt she hug him when they are saying goodbye to each other for if one dies or the two of them die. In other words, for if maybe they're not going to see each other anymore because something happens to one or the two of them. Now if my conclusion is correct then thats why they put many parts where we see them together and thats why they highlights those times when they are together to make us understand that they have became friends (or more hopefully or are about to become more than friends). They didnt have any Aang and Katara parts other than one so they are focusing more on Zuko and Katara now not Aang and Katara.

Now I saw the trailer again (Like a million of times) and I particularly focused of the part where they show Jun. On the background you can see Katara and Toph and a little bit after you can see Sokka next to Katara and Zuko behind them. They are all watching the fight but I dont see Aang. The hug happens in that episode because when they hugged the background is not the same or similar to the one in Ember Island Players episode and besides they are wearing Fire Nation clothing in the Ember Island Players and when they hugged they are not wearing Fire Nation clothing. So episode 316 happens when they are going back to the Fire Nation or are near the Fire Nation and episode 317 is when they are at Fire Nation in which they wear Fire Nation clothing. So when they hugged its either for when they are saying goodbye or at episode 316 in which Zuko probably does something that definitely changes Katara's mind about him and she maybe apologizes for the way she was acting towards him and then she hugs him.

The kiss:

The kiss happens in episode The Ember Island Players because that episode is the episode before the episode in which they go to war and obviously Aang would want to give her that "type of goodbye" before they go to war.