First I disagree strongly with this. In AL, it is clear both MC and the alive friend remained their whole life very affected by the event. It is moving on only in the sense of accepting to live with the grief so that they can allow to feel something else.
I preferred Melissa (by a lot), so I let Meghan died in my "canon" ending. And it really breaks her apart. Which leads me to the second part. I really disagree your point that they were "friends", which you are hinting is less a relationship that daughter/mother can have. Sometimes friends ties are more important than blood related.
That is particularly true for Melissa, whose family sucked. Meghan was her one true family, in some sense. And she now has to live her whole life with the feeling that "I'm alive because she is dead". That was what made such a strong emotion in the reader. That is why picking was so hard.
Which brings me back to a discussion I have a few days ago about how important choices must be in game. Real choices. Making that event a choice in the hands of the player is what for many it was soo hard. That is, in my opinion, one of the marvels of visual novels that I wished more developer focus on. Very few choices, but with a lot of emotional meaning, make for the best games.*
*of course many choices with a lot of emotional meaning would be fine, but we have to be realistic on the development process account.
And, just to mention, I don't mind kinetic novels, if the experience is equally good, though. But the effect of choosing outcomes and living with consequences is lost.
I am not saying it has to be something so copy paste: save one, let the other die. In fact, for me, there would be almost no question about which one to save.
The one I love, the one that is young, the one that I must protect as my job, they are all one and the same. That is, the choice for me, is absolutely obvious. SO, no, I wish it would be something else. But equally meaningful. No idea what, though, but something good that breaks your heart and drowns you in despair.
That is when a novel really touches you.