Well, I have to disagree here.
About Alena: I do not think she is perfect, she is actually still only 15. But for her age she is definitely one of the best at portraying distinct characters that I have seen in a skater for a while. To me it is very obvious that she is not restricted to one style, she can skate to many types of programs - etheral, light, soft but also be strong and fierce like in her SP last season or her Vampire exhibiton this season. What Alena can improve in, is showing more facial expressions, at the moment, she is mostly expressing the music through her body and movements. I don't see where she isn't portraying a character, though? It's very clear to me that she is Juliet in her FS and an angel in the SP. Even without music, this is very clear, the Juliet part probably more so than the angel one, since the latter is a pretty abstract concept. So, for me, she does both. Interpreting the music and portraying a character. She can't change the choreography she is being given. She can improve but for now it's obvious that she's above most of her peers in that aspect.
I like Sasha's personality, I think she's brave and cute and strong. But skating wise, I just do not see any kind of interpreting the music from her whatsoever. She neither expresses it with her body, nor her face and that's exactly the problem for me. She is doing the choreography she is being given and she does it well but that's it. I am really not good at explaining this but if you watch Alena (or Anna for that matter) you can see that they are moving their limbs beyond simple choreography, every fibre of their body matches the music, moves to it, down to the very tips of their fingers. Sasha does nothing like this, her whole body is stiff, besides the movements she was told to do, there is nothing that indicates that she actually feels anything of the music she is skating to. Her face in the beginning, when she is punching the judges, is blank. Where is the character? I see a young girl with amazing technical abilities who does her jumps to the music and a few choreographic moves and insane transitions in between. That's okay, it can still be enjoyable to watch but it should not warrant high scores in the performance and interpretation bit of the PCS mark, at least in my opinion.
That's why I feel what Sasha needs is either a tremendous improvement from her side, or programs that hide this. Her SP this season was good at this, it highlighted her strengths well. There wasn't a lot of portrayal of a character either but her power and the wow-effect of the 3Lz-3Lo matched to the music were enough to make it a pretty enjoyable program. Her FS however required her to show expressions, in order to bring a character from a movie many might not have seen to life. I did not see that. I have watched a few snippets of the fifth element out of curiosity. It was clear that Daniil watched the movie. His choreography matched some of the scenes. But Sasha? Again, she did what she was told to do. But I did not see a special connection neither to the character nor her music. I'm not going to say much about Big Spender because I do hope you're not suggesting she actually understood what she was skating to. It was a fun program and she was smiling but she had rightfully and thankfully no clue what the music was about.
As for PCS... In my opinion, the difference at JGPF of about 5 points between Alena and Sasha was about right, imo. I'm very well aware of the fact that this won't happen again, given that Sasha made multiple mistakes. So, yeah, your 1-2 points difference is likely what will happen. I do not agree with this. I think Alena is miles above Sasha in everything other than transitions. But that's how it's going to be.
I don't think it's that bad to criticize Sasha's artistry since this is the only thing she's really lacking in anyway. And she won't face any troubles whatsoever with the judges, her PCS will follow TES. So, I think we'll see her on top of most of the podiums next season as long as she keeps performing like she did this year. For me artistry and musicality are actually two of the most important aspects of figure skating and that's why I'm probably never going to enjoy Sasha's performances as much as those of some other skaters. But with the technical abilities she has shown so far, she should be more than fine anyway. And of course everyone is free to enjoy and like what he or she likes.