1. I usually try to redeem Kagha. Druids don't usually take life needlessly. Plus it feels really in character to have what is basically a philosophical debate with her over the druidic teachings that she clings to so fervently. She is purposefully twisting her own god's teachings to justify an act that goes against her true convictions because she's afraid. Showing her the error in her interpretation and resolving the conflict via words feels very druidy.
Of course a more aggressive "survival of the fittest" druid might decide that a lengthy debate won't solve anything and prefer just to take her life in a contest of might. Druids are not necessarily pacifists. They aren't even necessarily kind.
2. The Owlbear is not a natural creature. It was made by a crazy wizard and is a threat to the actual environment that it exists in, similar to an invasive species. Killing it is a very druidic thing to do because in taking its life you're preserving the stability of the local ecosystem to which it does not belong. Killing the cub would also align with druidic teachings because while it is an innocent life it cannot do otherwise but grow into just as destructive a force as its mother was. This is part of the whole "druids aren't necessarily kind" bit above. The standard druidic alignment is neutral, not good. A neutral character will do something that may be morally wrong for what they consider to be a greater overall good.
3. The only reason I can see a druid stealing the idol is to stop the ritual if the attempt to stop Kagha fails. Beyond that, it's a sacred druidic relic that belongs to this circle. Stealing sacred artifacts from your fellow druid is generally considered "A dick move".
