@MagpieGD Ugh, so hard to do this. I just killed off a character in a story I'm working on, and it was heartbreaking. I reread the scene, and I actually got teary-eyed.
Is the death needed in order to progress the plot? If so, I say go for it. Tragic events can often spur a character on to do things or become someone they wouldn't have dreamed of had it not been for what happened.
If it's more for the emotional impact and won't change the direction of the plot, then don't off them. If you like them enough and don't wanna see them go, don't do it.
Of course, you could change the original direction of the plot to keep them in it. You're the writer. You call the shots. All right, we writers think we call the shots, but we know it's really the characters in charge >_>