Whatever you think happened, happened.
Seriously. That's canon.
There are probably hints somewhere in the season that would explain it; will have to re-watch it later.
She's clearly spiritually gifted, and was able to reveal/guide Korra to the existence of Raava in Vaatu.
Wow.... this is literally the most glowing review of Book 2 I've read. Glad you enjoyed it, most people would have said the opposite.
I can see why people would have issue with Korra's early characterization, but I felt her actions were justified given the way her father and Tenzin conspired to keep her in the compounds.
Her uncle showing up and defeating the spirits that took down Tenzin and Tonraq naturally pushed her closer to her uncle (Tenzin was pretty ineffective as a spiritual guide lol).
Her lashing out at Mako in the police office was also understandable given the situation she was in (her people in Civil War/no help from the UN forces).
If anything, it reminded me a bit of the Israeli/Palestinian issue in some ways; people can be irrational given the circumstances :/
It was notable how she mellowed out after her glimpse into Wan's life and his struggles as the Avatar; it felt like she matured after that.
Season Two is well done.