I'm assuming most junglers use the same rule of thumb as myself,
If your ADC is carrying hard and has a much larger impact on the game than yourself then I freely give red buff, I even tank it for them. Same for mid lane and blue. However if it's equal or I'm ahead then it's mine, the buffs are nice but it's also a source of gold worth more than 2 cannon minions and XP. Laners throw a tantrum if I take a lane minion so why wouldn't I want MY XP and GOLD SOURCE?!
Also you said the Shyv was 0-6, what was her assist #? If it's 0-6 and the number of kills YOU have or even more then it sounds like she did the diving and sacrificing while the carries cleaned up and that 0-6 doesn't look so bad any more. Getting the killing blow means nothing except epeen stroking rights.