(I decided to stick with the character having a punctured lung, but change it slightly so that the other characters don't find her until it's too late and she's already dying.)
1. How much would a stab-wound of this type bleed externally? (Especially after moving around for about half an hour afterwards.)
2. Would it be physically possible to pull a knife out of your own back, if it was high enough up to pierce your lung?
3. Aside from an increasing difficulty in breathing, presumably coughing up blood, and eventual death, what other effects would this kind of injury have? (Things caused by the blood loss, for example...)
(As you can most likely tell, I don't often write characters getting violently killed, so apologies for all the probably stupid questions!)