OC-SI Reincarnated as Roxy.
Roxy wasn't always Roxy. Once, she was a broke college student who spent way too much time watching cartoons than she should have, until naturally everything went to shit and she died. Now she's a character she didn't even like that much in one of those cartoons, and she's left with a choice; she can either A, be a good little cliche fanchild and try to be as helpful to the Winx Club as possible, or B, shamelessly abuse the fact she has both foreknowledge AND highly powerful magic to make the most of her new life free from her previous burdens, doing whatever the fuck she wants for shits and giggles.
She chooses option B.
(Or in which, Roxy is unhinged, the plot is in shambles, the Winx Club and Trix are guys for some reason, Valtor is extremely confused, plot holes get filled, Riven gets appropriately dunked on and Faragonda is driven to alcoholism. Extreme crack ahead, tread with caution)