GuardiaStar

This mostly pertains to the THG films (I've read the books)
I get why she falls for Peeta.
I think also initially she wanted to be with Gale, (before the reaping) and loves Gale in a certain way but Katniss is drawn to Peeta. And they kind of work (of course ) because they're both freedom fighters. They want to help people and save lives. Don't get me wrong Gale is a rebel too, and is willing more than willing to save lives but he wanted to stay in the Districts than actually be out there with Katniss (just a thought).

AtomicEmpress

I think Gale is more war minded when it comes to his rebellion, he wants to hurt the captiol. Whereas Peeta wants to help the people of the district. Thats why Peeta's turn because of what the captiol did to him is so surprising and upsetting because he is so not violent.