I think this may be a matter of opinion; different psychologies will answer differently.
Personally, my characters feel real to me; but I remind myself of a few things. I go back over what I wrote for her, reminding myself that I invented her, all she really consists of is these words on paper. It is like sketching a person, then burning the sketch. In reality, I kill ALL the characters, sooner or later, when I stop writing about them. They will have their last words, even if I write a series.
What I would like to do for her is give her a meaningful death; I am not just killing her to get her out of the way. Her death will motivate the characters that love her, even if on the surface it looks like a pointless death, it will mean something in how the future of her friends turn out.
You have already said she is kind and caring -- Is she brave enough to knowingly sacrifice herself for her friends? If somebody must die, does she love them enough to make it herself? I think, for the other characters, realizing somebody loved you that much is a powerful emotion that can motivate them to risks and sacrifice they would not have made without her "going first".
Personally I don't kill "good side" characters with stray bullets or other such random events or accidents; if they die, they die fighting. I pay a lot of attention (and often rewrites) to deaths so they will be meaningful and impact the story. And even if the death is meaningless, it can still have an impact upon the characters left behind to grieve and perhaps avenge her. if it doesn't -- You probably did not need this character in the first place.
Second, if I have become attached, that is a good thing. It means you didn't write a cardboard character to kill and forget, just to make a point. Hopefully the reader is also attached, so her death will be meaningful to them.