1. Given that we don't know which sort of circle MC is from, siding both with and against Kagha shouldn't be a problem.
However, there is a special reward only gainable through her death, and a different special reward only achieveable if you redeem her.
2. I couldn't bring myself to harm it with my druid, *but* druids don't normally consider monstrosities animals. You can do either again.
3. I don't think this sort of thing is easily RP able unless you have a chaotic evil character, or some very special backstory.
Druids get their magic from the gods (though they don't necessarily know it). Silvanus is one such god. Druids don't normally want to harm those. Or another good/neutral aligned circle, for that matter...