the murder (not a freely made choice by the girl) in AL isnt really comparable,. and imo, made the game into the masterpiece and #1 AVN to date, that it is.
having said that, it wouldnt work in this game. MC has invested into her, and tried his hardest to save her. if she does go through with it (of course she wont) then MC should have zero feelings about that, or at most, feel the loss of a serious emotional investment, nothing more.
no one is taking anything from her, she is giving it up willingly, we should respect her wish to die.