Karen is informed by owl that she's a prefect. She writes her friends about that, of course.
"People'll just assume she's a Squib -?"
(Catherine pats her papa's cheek and now he has lemon sauce on it.)
"Yeah. But we don't want her expecting a letter, so we're going to explain as soon as she's old enough to understand -"
"It's vanishingly unlikely. I did check that the birth father wasn't a wizard - so I could duel him, mostly, but also so she'd know -"
"...the official story would have required conduct that would have been very out of character for both of them, so I concluded it was probably a lie, checked that no one involved was presently being unduly pressured somehow, and then decided they'd explain themselves when it suited them?"
"I would personally be upset if people thought I was irresponsible enough to have created such a situation but -"
"I was a little worried you'd all feel like you'd been - pressured into loving Catherine more than you would've -" says Rebecca.