I rather like it.
Jessica has shown twice that she's prepared to stand toe to toe with Eva in an argument, and though they're usually pretty innocent of anything, I wouldn't have minded if the kids were a
little more involved with family affairs than they are.
honestly, though, if Jessica figured it out (and that's a pretty fair possibility), I mostly imagine her ... weakly asking her parents about it in a roundabout way (Is... is Grandfather really alright, shut up in there all the time..?), and more or less convincing herself to believe the lie they'd almost certainly tell.
But no yeah, somebody go write this blackmailer-Jessica forgery, right away please.
