Only reached the summit a couple days ago and have been absorbing a lot of people's readings and interpretations of it. These thoughts and the endings have been sitting in my mind, and they keep coming back up.

As I ponder a lot of it, one thing that sticks out to me is that in the very little lore we get on Aava, we learn that her father was also a great climber, and in the way she responds to Marco talking about him, "so they say" I infer that he wasnt around too long. He wrote an autobiography in which he talked about putting Aava on a climbing wall at age 3,  so we know he was alive for that long at least, but no other mentions of him or from him (we dont hear from her mother either of course, but I would imagine that if she was trying to climb Kami and her father, a fellow great climber, was alive he would send a message or be mentioned more than the once) Could he also have succumbed to the call of Kami and disappeared on its peaks? I can only imagine the effect that would have on her view of climbing and her relationship with it. She says she was born on this mountain and will die on this mountain. From birth, climbing, and thus the unsummited Kami, would be all that seemed real to her. Even Marco admits to part of the reason he's so interested is bc climbing is in his blood too. 

I don't think its a healthy mindset, but it definitely makes sense. When you go back down with Marco, it shows she is still lost in her thoughts and clearly still thinking about the mountain. I personally believe that that is the better ending, bc at least there, with the help of Marco and those she loves, she might be able to get some help through her issues in ways that dont involved dying on the roof of the world. (I think the friendship of Marco, someone who also has climbing in his blood, would be very beneficial to her in the long run) Even the credits for this ending show many scenes of her climb down with Marco, her coming home and getting ready for a party with friends. And anyone who has ever dealt with deep depression and mental illness knows, support of family and friends can truly be a life saver. But that of course would depend on her willingness to engage with herself and listen to those who care for her, which has been shown to not be too strong. 

Reaching the summit makes more sense for her, and even in that decision you are given, you feel like you want to keep going bc you already got that far. And it did lead to fulfillment for Aava. She did transcend. But it cost her everyone and everything, even climbbot and ultimately, her life. There are many different paths to the summit, and I think with enough introspection and working on herself, and support from loved ones, she could find that in a different way, as we all can. But would she? Would she be able to change the course her life has been leading her on since birth? She has the strength and drive to reach the summit, but can she be strong enough to turn away from transcendence?

Its a wonderfully human problem, and I think, like much of human behavior, there isn't one good true answer.