It sounds shady if you're looking for shade, but she's just saying that the stuff she was being sent wouldn't be authentic coming from her, considering her age. Charli is like a young Gwen, so that's probably why she used her as an example.
Jesus it just means that the songs presented to her were not her "sound" anymore and that it was better suited to someone younger like Charli. Stop trying to paint comments as massive shade.
Lol I don't see any shade at all! It felt weird and fake to Gwen, because the original album wasn't where she was at the moment. Charli and her still coo'