Come on Aoyama-sensei. This is the modern day. Use digital technology, they exist!! Age-up filters already exist for photos, so just have someone develop a filter that works even with video calls.
Audio and video goes out of sync all the time if there's bad network so it doesn't matter if there's a glitch.
How the hell did she miss the dying message, it's literally right there. Not like this culprit was in a hurry or anything.
But then again, this culprit had no chance to begin with, seeing as the reason that she was found out to begin with was due to a girl happened to go inside that particular abandoned building, she just happened to bring something akin to luminol, and she just happened to have a detective boyfriend.