The antler of the stag (Baratheon) impaling/killing the direwolf (Stark). It symbolic/foreshadowing via the house sigils...

1) Dany getting in the tub while being warned that the water was too hot, very much like walking to the fire as the dragon eggs are hatching.
2) The pin that Dany wears with the three-headed dragon.
3) As mentioned above, the stag horns impaling the direwolf. Although arguably the Lannisters kill Ned (Joffrey/Cersei), it is Robert who starts the wheels in motion.

There is a lot in store for the young lady over the next few books so definitely read them. Like all characters, my attitude of her was constant subtly shifting throughout the books.

I've read all four, and I still despise her. She's basically Cersei if Cersei was stupid and cowardly. I didn't even have any sympathy for her when she was getting abused by the Lannister lackeys - after they whacked her dad, if she'd had even a shred of decency and honor she should have stabbed Joffrey in the eye with a fork and then thrown herself out of the nearest tower. She is far and away my least favorite, and the least interesting, major character. The chapters that focus on her are endurance tests. Especially in the last book.