If you have the opportunity to save a life at the expense of ending another, what would you do?

This is a personal dilemma I am currently facing, and I need advice.<br><br>My girlfriend is in a very bad car crash, and I need to save her life by putting a knife in her heart. However, by doing so, I would have to end the life of an innocent woman who is standing nearby. She is pregnant and has a 2 year old child who will grow up without a mother if I don't save her.<br><br>What do you think I should do?