Why Doesn't Katniss End Up With Gale?

The reality of why Katniss doesn't choose Gale is because he killed her sister, indirectly. Coin decided to blow up a ton of Capitol children during the siege of the Capitol and Prim was there trying to help the children at that time. The bombs they used were designed by Gale and BeeTee in the base in district thirteen. Coin made sure that Prim was in the cage full of children at the time of the bombing so that Katniss would see this and think that it was all President Snow's fault. Coin was always afraid of Katniss becoming the President so she needed Katniss on her team to assassinate President Snow so that Coin could become president. All this said, Gale was working closely with Coin so after the bombing Katniss could not look Gale in the eye without the thought crossing her mind that he probably was the reason for the death of her sister. It is very twisted and a sad way for their 'romance' to end. Peeta ends up being the one that 'she cannot live without.'