That's the thing tho, what if Lucia's absence is a deliberate choice?
Think about it, Lucia is the only person in the house "in the know" alongside the MC, imagine what she'd do if she suddenly found out he had gone blind and deaf after snooping in his grandfather's room, grandfather she knows is planning destardly shit on everyone in the house too.
She'd probably bail. She's not close close enough to the MC yet to plan bloody vengeance, that would be more Catherine's speed, she'd choose survival over it and bail, just like she did in the Coma bad ending, where she returns home as soon as shit starts hitting the fan too.
Tiff should also not be here since she was there when Hunter crippled the MC, so you'd expect her to rat on him, except you can argue after Hunter caused the incident with Sterling, he simply played it out as the concerned Grandfather who was, like, trafficking drugs to keep his family afloat, and think about it, Tiff needs money, money Sterling can't give her anymore, meaning she'd succumb to Hunter out of necessity more than anything else.
You could also argue that, post chapter 10, since the MC is now her "fix" for a legit circadian rhythm, she'd probably be less self serving in this scenario and maybe even plot vengeance, or she might also fall more easily victim of Hunter since he would be her "provider," fill the "vacuum" left by the MC, so to speak.
Not even that difficult to do it honestly. Like, just provide Catherine with proof Hunter blinded the MC before he gets to her, next thing you know dude has been defenestrated and there are no witnesses to prove it thanks to Lucia.
(Side note, speaking of Lucia, I don't know how familiar is the author with Italian stuff, but "there is nothing more divine than fucking your cousin" (Divina and Cugina rhyme in italian) is an... extremely old joke about incest here in Italy, something Hunter would have heard back in Italy in his youth, which makes Lucia being Sterling's Cousin Times Two a great way to have this very same joke happen).
