Because I should not answer in comments, here are some suggestions and ideas:
First of all, as @RavenDreamer commented, her personality traits likely matter a lot here. A honest person likely is much harder to convince to look the other way than a cynical one.
Have you tried giving her a reason to spend the hook on? E.g. if you raise her taxes using your hooks on her, maybe she'll use her hook to lower them back.
If nothing like that works, killing her to cover your tracks might be the only option left. Although that may the start of your highway to hell, when during the next feast... ;)
The bottom line of course is: Don't do the crime if you don't want to face potential consequences. Or at least, don't go to feasts while your murder plan is executing to minimize the risk.
I like it that CK3 always forces one to weight the advantages against the disadvantages. There barely seems any free lunch in the game - even a free feast can have negative side effects! :)