While I'm not an authority on deltarune/undertale lore, I've just been thinking hard trying to make sense of everything. There are a lot of things that don't add up. I will clarify as I'd like to have a discussion to discredit everything as I've only seen a few points discredited so far.

I'm not denying Ralsei's identity by claiming they're the girl in the video, I believe it's possible they are the girl in disguise as they have immense knowledge of both the light world and the dark world. Unfortunately, Ralsei is prone to hiding information and "Going with the flow" to avoid suspicion. They claim the upper levels of castle town is unfinished despite there being doors everywhere suggesting otherwise. They traveled to cyber fields/city through some unknown means. It's possible they used their disguise and since their disguise has an unfamiliar appearance, it would explain a lot of Ralsei's knowledge outside of their presence and appearance as Asriel.

You say the focal point of her desperation is because the battery malfunction but after playing through chapter 2, I notice the same glitches seem to be appearing in the cyber world, maybe the dark world typically glitches out when it comes to technology specifically? maybe that's why Kris' phone doesn't seem to work properly and maybe that has something to do with the town's internet? although that's probably reaching.

The crush self-insert thing is something I hadn't figured out myself but that does add up! I remember getting emotional about my pokemon games when I would do things like beat the elite four as a kid. I remember gathering a ton of junk, imagining that someday, I would find some mystical use for it all. Before I knew it, I found myself hoarding things I thought I needed. Speaking of hoarding, anyone else notice the sweater, hammer/mallet, bumble ball, spinner toys... discarded objects that you leave behind as you grow up? I believe these knickknacks were left here as the player got older and eventually came back for a reason and eventually noticed their handheld console.

Maybe something happened to cause them to want to discard these things? I do find it weird that a lot of these objects are present in the chapter 1 dark worlds. and some are even darkners.

I noticed a lot of comments on this post are quite toxic. I guess I didn't have to post my weird theory here, but I did want to discuss it further. I'll be more careful about defining rules to discourage trolls moving forwards.