There's probably no good reason, she's not exactly smart. She does a lot of things that make no sense or is just stupid. Like in one of the last cooking streams she literally did her makeup and everything and took a selfie for the thumbnail but then hid her face for the whole stream :OMEGALUL:
But if I think harder about it, I remember her saying something like, VTuber models should always look like the irl person otherwise there's no point, and the VTuber community got mad at her for that one lol. She's obsessed with wanting to cosplay her avatar at a con someday too, and her whole style's based on gravure models, Japanese fashion, and anime poses. So maybe she wants her pics to look more like "irl anime" and her VTuber to look more like herself. But the way she's trying to do it just looks terrible and weird
There's also the fact she copies other people all the time. Like Silver cosplays her VTuber at cons, maybe that's why she wants to too. So she might just be trying to copy the way someone else filters their pics